Amin Dharmeshkumar v Secretary of State for Housing, Communities and Local Government & Anor

MR TIM SMITH (sitting as a Deputy High Court Judge) : Introduction

1. This is an appeal by Mr Amin Dharmeshkumar (“the Appellant”) against a decision of a Planning Inspector appointed by the First Respondent Secretary of State (“the SoS”). The appeal is brought under section 289 of the Town & Country Planning Act 1990 (as amended) (“the 1990 Act”).

2. The Inspector’s decision related to an appeal by the Appellant against an enforcement notice served on him by the Second Respondent (“the Council”). There is also a challenge to a separate but related decision by the Inspector on the costs of the appeal, but for ease I refer to “the claim” (singular) as encapsulating both challenges unless indicated otherwise.

3. The substance of the enforcement notice and the subsequent appeal touch on some areas that are important to the operation of planning law, not least questions around what works constitute “development” within the meaning of the 1990 Act, the interpretation of a written planning decision, and the proper exercise of permitted development rights. Background facts

4. The Appellant is the owner of a site formerly known as 6-10 Hallmark Trading Centre, Fourth Way, Wembley. The site accommodates a three-storey building (“the Building”) that was formerly in use for office purposes.

5. In response to separate applications the Council made two decisions in relation to the Building, both on 27 th December 2017. The decisions were as follows: i) The grant of planning permission for “Installation of bike store to rear of building and replacement fenestration with timber cladding between first and second floor windows to both front and rear elevation of building (revised description)” (“the 2017 Permission”), and ii) A prior approval decision reference 17/4679 (“the Prior Approval”) for the change of use of the Building, pursuant to permitted development rights granted by the Town & Country Planning (General Permitted Development) (England) Order 2015 (“the GPDO”), from a use as offices to a residential use.

6. The 2017 Permission was granted subject to two conditions. Condition 1 was a standard condition requiring development to commence within 3 years of the date of grant. Condition 2 (with its accompanying reason) was in the following terms: “The development hereby permitted shall be carried out in accordance with the following approved drawing(s) and/or document(s): DA/BRENT/PLN-PRO/2017/16-I, DA/BRENT/PLN-EXI/2017/015, PL/01-I, Location Plan Reason: For the avoidance of doubt and in the interests of proper planning”.

7. In relation to the Prior Approval, it suffices for the purposes of this factual background to note that the GPDO grants a deemed planning permission for certain classes of development, including certain material changes of use, that would ordinarily require the grant of an express permission. In some cases the exercise of the permitted development rights is subject to the proposed developer seeking from the local planning authority either confirmation that no prior approval of certain details is required or, if it is, that prior approval of those details is granted. The permitted development rights for a material change of use relied upon in this case are rights found in Part 3 Class O of Schedule 2 to the GPDO. They are rights which incorporate the prior approval process that I have described.

8. The Prior Approval decision was made by one of the Council’s planning officers acting under delegated powers. It was stated to be on the following terms: “I refer to your application dated 01/11/2017 proposing the following: Prior approval for change of use from offices (Use Class B1(a)) to residential (Use Class C3) involving the creation of 12 x flats And accompanied by plans or documents listed here: DA/BRENT/PLN-PRO/2017/09-J, DA/BRENT/PLN-EXI/2017/018-J, PL/01-J, Location Plan At 6-10 Hallmark Trading Centre, Fourth Way, Wembley, HA9 0LB Determined by the Local Planning Authority that the PRIOR APPROVAL of the Authority is REQUIRED and hereby APPROVED.”

9. Thus it will be seen that the Council’s determination of the prior approval application was in two parts: (a) that a prior approval of certain details was required, but (b) that the prior approval was granted in accordance with the submitted details.

10. The Prior Approval also attached an Informative which stated as follows: “The applicant is advised that the bike store approved as part of [the application for the 2017 Permission] shall be completed prior to the implementation of this prior approval consent. The two consents shall not be carried out in conjunction with one another”.

11. On 18 th August 2018 the Council made a direction under Article 4 of the GPDO. This had the effect of removing, from that point onwards, the permitted development rights conferred by Schedule 2 Part 3 Class O to the GPDO on sites which fell within a “Strategic Industrial Location” as designated by the Council. It is common ground that the Building falls within such a location, and that Class O permitted development rights are no longer capable of being exercised in relation to it.

12. In November 2019 the Appellant began works to remove the external facades to the Building, in reliance on the 2017 Permission. Further works were undertaken by the Appellant to remove and replace the roof and its supporting structure, the replacement of all the windows on the first and second floors, the removal of a shuttered access to the rear of the Building, the replacement of three existing staircases with two new ones, and the removal of internal partitioning to the first and second floors resulting in an altered internal configuration to the building.

13. On 4 th May 2020 the Appellant’s architect made a written request to the Council to approve amendments to the plans approved by the Prior Approval. Paragraph W to Schedule 2 of the GPDO allows for such requests to be made. In this instance the formal request followed a period of pre-application discussions between the architect and the Council’s case officer. The Appellant’s case is that its written request for approval to amendments was made following a request by the Council’s Housing Department, which at the time was exploring the possibility of taking a lease of the twelve flats to be constructed in the Building but only after some alterations were accommodated.

14. The Council failed to respond to the Appellant’s request of 4 th May 2020. As a result, in the period between May and September 2020 the Appellant made further requests for amendments. These were requests by either email or by formal applications under (respectively) section 73 and section 96A of the 1990 Act.

15. The responses from the Council to these various attempts at authorising amendments were either to refuse them formally or to fail to respond at all.

16. On 2 nd November 2020 the Appellant submitted a planning application under section 73A of the 1990 Act to vary, retrospectively, condition 2 on the 2017 Permission. This would allow for changes to the fenestration from those details approved by condition 2. On 21 st December 2020 the Council refused this application, giving as its reason “The changes to the existing building do not relate to the original approved via [the 2017 Permission]”.

17. Permitted development rights for material changes of use under Part 3 Class O are deemed to be granted subject to a number of standard conditions. One of these requires that any material change of use taking place in reliance on the permitted development rights must commence within 3 years after the date of the Prior Approval (i.e. in this case by 27 th December 2020). On 24 th December 2020 the Appellant’s architect sent an email to the Council in the following terms: “We refer to prior approval ref 17/4679 and confirm that the material change of use from office to residential of the first and second floors of this building has been implemented”.

18. Meanwhile on 23 rd December 2020 the Appellant had made a further retrospective application under section 73A for “Changes to front and rear elevation fenestration and installation of cycle store to rear of the building and internal layouts”. The Council refused to validate the application. The Appellant therefore appealed against the non-determination of the application. On 22 nd September 2022 an Inspector appointed by the Secretary of State allowed the Appellant’s appeal. The description of the permission thereby granted was for “changes to front and rear fenestration and installation of cycle store to rear of building”. The Inspector also made an award of costs against the Council.

19. The twelve flats in the Building created by the Appellant’s works were occupied on 19 th April 2023 pursuant to a tenancy agreement.

20. On 7 th August 2023 the Council served an enforcement notice on the Appellant alleging a breach of planning control (“the Enforcement Notice”). The alleged breach was described as “without planning permission, the material change of use of the land/premises to twelve flats”. The Enforcement Notice required the following action to be taken by the Appellant in accordance with specified timescales: “STEP 1: Cease the use of the premises as flats. STEP 2: Remove all partitions, toilets, bathrooms and kitchens from the premises. STEP 3: Remove all items, materials and debris, associated with the residential use from the premises. … TIME FOR COMPLIANCE: 6 months after this notice takes effect. … WHEN THIS NOTICE TAKES EFFECT: This notice takes effect on 16 September, 2023 unless an appeal is received prior to the effective date”.

21. The Appellant appealed against the enforcement notice on three grounds. The grounds correspond with various sub-paragraphs in section 174(1)(a)-(g) of the 1990 Act, and were as follows: i) Ground ‘c’ - that the activities did not constitute a breach of planning control, specifically (in this case) because the material change of use was deemed approved by a combination of the 2017 Permission and the exercise of permitted development rights under Part 3 Class O to the GPDO; ii) Ground ‘f’ – that the steps required to be taken exceeded what was necessary to remedy the breach of planning control; and iii) Ground ‘g’ – that the period allowed for compliance was unreasonable

22. The Appellant’s enforcement notice appeal was heard by Martin Allen, a Planning Inspector appointed by the Secretary of State (“the Inspector”), at a public inquiry on 23 rd and 24 th April 2024. The Inspector also undertook a site visit on 24 th April.

23. By his decision letter dated 2 nd October 2024 (the “DL” ) the Inspector dismissed the substantive appeal, although in response to the ground ‘g’ appeal he extended the time period allowed for compliance with the Enforcement Notice from 6 months to 12 months. Subsequent references in this judgment to “DL#” are references to paragraph numbers in the DL

24. The main focus of the appeal, though, had been on the ground ‘c’ appeal. Having summarised the works that had been undertaken to the Building, and having then set out a summary of sections 55(1), (1A) and (2) of the 1990 Act, the Inspector’s core conclusions regarding ground ‘c’ were that the works went beyond what could properly be considered to be works of repair and/or alteration, and that they constituted “development” for which planning permission was required but had not been obtained.

25. Part of the Inspector’s conclusions on ground ‘c’ related to an ambiguity identified on the face of the Prior Approval regarding the plans said to be approved. The Inspector described the issue, the arguments of the parties, and his conclusion on this point, in DL16-18: “16. Immediately prior to the Inquiry, the appellant raised an additional matter in respect of the drawing numbers that are referenced within the [Prior Approval], in that two of the drawings referred to are incorrect. In fact, it was accepted by the Council’s witness at the Inquiry that the cited plans do not exist.

17. In my view, this creates ambiguity within the decision notice as to what plans are to be referred to. In such circumstances, it is permissible to consider extrinsic evidence outside of the decision notice itself. In this case, this would include the details that were submitted with the application, i.e. the floor plans showing the layout of the units. This would therefore indicate that the development should have been carried out in accordance with those details. It is also pertinent to note that at all times the appellant was in no doubt as to which plans were required to be complied with, having made attempts to seek agreement to depart from them.

18. It has also been put to me that as the description of the development simply refers to the creation of 12 flats, essentially that any scheme comprising 12 flats would have been permitted. I do not accept this. While Class O of the GPDO contained no requirement for the floor plans to be submitted, the appellant chose to provide them. These details were considered by the Council when making its decision. It was on the basis partly of these details that the Council granted prior approval. As such, the floor plans are relevant and should be adhered to”.

26. The Inspector’s overall conclusions on the ground ‘c’ appeal are captured in DL22-24, as follows: “22. It was put to me at the Inquiry that these works comprised repair and/ or alteration, that some of the works affected only the interior and those that affected the exterior did not materially affect the external appearance of the building. However, from the description of the works together with the visual extent of the works depicted in the photographs, I am of the view that the works that were undertaken to the building went beyond mere repair and/ or alteration. They were substantial and extensive works of rebuilding and were structural alterations, which are sufficient to comprise building operations in their own right. As a result of this, I find that they do comprise development, and are not excluded from being so by section 55(2) of the Act.

23. These works were undertaken in the course of developing the building so that it could accommodate the proposed change of use, which was granted prior approval by the Council, and thus before the change of use began. The change of use is granted planning permission, following the grant of prior approval, subsequent to Article 3 of the GPDO. However, paragraph 5 of Article 3 states: “(5) The permission granted by Schedule 2 does not apply if– (a) in the case of permission granted in connection with an existing building, the building operations involved in connection with that building are unlawful; (b) in the case of permission granted in connection with an existing use, that use is unlawful” [22/24.] In light of my findings above, that the physical works that were undertaken to the building were of such an extent as to comprise development, and that no planning permission was obtained for them, these works are unauthorised and thus unlawful. As a consequence of this, the appellant is not able to rely on the scheme which was given prior approval. Note that there is an error in the numbering of paragraphs in the DL. What should be paragraph 24 is shown as a second paragraph 22, with the numbering re-setting at that point to 22 … Overall conclusion on ground (c)

24. The development of the site was not carried out in accordance with the approved details. There was no agreement to any variation. Even if there had been agreement to change the scheme, the physical works were such that they required planning permission, which was not obtained. Thus, these works to the building were unauthorised, meaning that the appellant cannot benefit from planning permission granted by the GPDO in any event. Accordingly, there has been a breach of planning control and the appeal under ground (c) must fail”.

27. At the inquiry the Appellant had made an application for costs against the Council. The Inspector issued a second decision letter in relation to the costs application (the “CDL”), also on 2 nd October 2024, in which he made a partial award of costs in favour of the Appellant. The partial award was “… limited to those costs incurred in dealing with the matter of seeking the written variation of the approved plans …”.

28. The Appellant sought permission to appeal the two decision letters to this court. The grounds of appeal against the substantive decision to dismiss the appeal against the Enforcement Notice may be summarised as follows: i) Ground 1: this ground compromises several sub-elements, namely that the Inspector: a) Erred in his interpretation of section 55 of the 1990 Act, in particular in his conclusion that the exception to the definition of “building operation” in section 55(2)(a) did not apply. Properly construed, the works undertaken to the Building were works of “maintenance, improvement or other alteration” and hence the Inspector’s conclusion that they were works of development requiring planning permission was wrong in law; b) Erred in law in how he construed the effect of the retrospective planning permission alongside Article 3 of the GPDO, and consequently erred in law in his finding that the works undertaken to the Building were unlawful; and c) Erred in his interpretation of Article 3(5) of the GPDO, in concluding that because the works in question had not “become lawful” through the expiry of time or the grant of a Lawful Development Certificate under the 1990 Act, they were therefore “unlawful” ii) Ground 2: having accepted that there was some ambiguity on the face of the Prior Approval, because it referred to plans or drawings which all parties agreed did not exist, the Inspector erred in law in finding that the ambiguity could be resolved by reference to extrinsic material iii) Ground 3: the Inspector erred in his interpretation of paragraph W(12) of Schedule 2 to the GPDO, by finding the Appellant not to have complied with the terms of the Prior Approval despite his separate finding that the Council had been “blatantly unreasonable” in refusing to engage with the Appellant over his attempts to vary the terms of the Prior Approval

29. In relation to the CDL, the Appellant’s appeal is parasitic on Ground 1 of the appeal against the substantive decision. The Appellant submits that if Ground 1 succeeds, because the Inspector’s conclusion that the unlawfulness of the works undertaken to the Building cannot stand, then necessarily his conclusion not to award the full costs of the appeal against the Council must also be unlawful.

30. By virtue of section 289(6) of the 1990 Act, appeals of this nature require the permission of the court before they can proceed. The question of whether to grant permission was considered at an hearing on 28 th November 2024 before Karen Ridge (sitting as a Deputy High Court Judge). In a reserved judgment ( [2025] EWHC 169 (Admin) ) Ms Ridge granted permission for grounds 1(a) and 2 of the substantive appeal to proceed, refusing permission for the other grounds. Recognising the parasitic nature of the appeal against the CDL, Ms Ridge also granted permission for that appeal to proceed.

31. On this basis the appeals came before me for substantive hearing.

32. The Second Respondent, although appearing at the permission hearing before Deputy High Court Judge Ridge, elected not to participate in the substantive hearing (as is its entitlement). Relevant law

33. Section 289(1) of the 1990 Act provides as follows: “289 Appeals to High Court relating to certain notices (1) Where the Secretary of State gives a decision in proceedings on an appeal under … Part VII against an enforcement notice the appellant or the local planning authority or any other person having an interest in the land to which the notice relates may, according as rules of court may provide, either appeal to the High Court against the decision on a point of law or require the Secretary of State to state and sign a case for the opinion of the High Court. … (4A) In proceedings brought by virtue of this section in respect of an enforcement notice, the High Court or, as the case may be, the Court of Appeal may, on such terms if any as the Court thinks fit (which may include terms requiring the local planning authority to give an undertaking as to damages or any other matter), order that the notice shall have effect, or have effect to such extent as may be specified in the order, pending the final determination of those proceedings and any re-hearing and determination by the Secretary of State. … (6) No proceedings in the High Court shall be brought by virtue of this section except with the leave of that Court and no appeal to the Court of Appeal shall be so brought except with the leave of the Court of Appeal or of the High Court”

34. Section 55 of the 1990 Act provides, so far as is relevant to the facts of this case, as follows: “55 Meaning of “development” and “new development”. Subject to the following provisions of this section, in this Act, except where the context otherwise requires, “development,” means the carrying out of building, engineering, mining or other operations in, on, over or under land, or the making of any material change in the use of any buildings or other land. (1A) For the purposes of this Act “ building operations ” includes— (a) demolition of buildings; (b) rebuilding; (c) structural alterations of or additions to buildings; and (d) other operations normally undertaken by a person carrying on business as a builder. (2) The following operations or uses of land shall not be taken for the purposes of this Act to involve development of the land— (a) the carrying out for the maintenance, improvement or other alteration of any building of works which— (i) affect only the interior of the building, or (ii) do not materially affect the external appearance of the building”

35. The GPDO was made pursuant to the powers of the SoS in section 59(1) of the 1990 Act. Article 3 of the GPDO provides as follows: “3 Permitted development (1) Subject to the provisions of this Order … planning permission is hereby granted for the classes of development described as permitted development in Schedule 2. (2) Any permission granted by paragraph (1) is subject to any relevant exception, limitation or condition specified in Schedule 2. (3) References in this Order to permission granted by Schedule 2 or by any Part, Class or paragraph of that Schedule are references to the permission granted by this article in relation to development described in that Schedule or that provision of that Schedule. (4) Nothing in this Order permits development contrary to any condition imposed by any planning permission granted or deemed to be granted under Part 3 or Part 13 of the Act otherwise than by this Order. (5) The permission granted by Schedule 2 does not apply if— (a) in the case of permission granted in connection with an existing building, the building operations involved in the construction of that building are unlawful; (b) in the case of permission granted in connection with an existing use, that use is unlawful”.

36. Article 4 of the GPDO provides as follows: “ Directions restricting permitted development

4. —(1) If the Secretary of State or the local planning authority is satisfied that it is expedient that development described in any Part, Class or paragraph in Schedule 2, other than Class DA of Part 4 or Class K , KA or M of Part 17, should not be carried out unless permission is granted for it on an application, the Secretary of State or (as the case may be) the local planning authority, may make a direction under this paragraph that the permission granted by article 3 does not apply to— (a) all or any development of the Part, Class or paragraph in question in an area specified in the direction; or (b) any particular development, falling within that Part, Class or paragraph, which is specified in the direction, and the direction must specify that it is made under this paragraph. (2) A direction under paragraph (1) does not affect the carrying out of— (a) development permitted by any Class in Schedule 2 which is expressed to be subject to prior approval where, in relation to that development, the prior approval date occurs before the date on which the direction comes into force and the development is completed within a period of 3 years starting with the prior approval date; …”

37. Class O of Part 3 to Schedule 2 of the GPDO provides that permitted development rights exist for material changes of use, including development on the specified terms and subject to a series of conditions. The version of Class O which was reproduced in the authorities bundle came into force in August 2020. It therefore post-dated the Prior Approval that was granted in 2017, although nothing here turns on that fact. Class O now provides as follows: “O. Development consisting of a change of use of a building and any land within its curtilage from a use falling within Class B1(a) (offices) of the Schedule to the Use Classes Order, to a use falling within Class C3 (dwellinghouses) of that Schedule. … Conditions O.2—(1) Development under Class O is permitted subject to the condition that before beginning the development, the developer must apply to the local planning authority for a determination as to whether the prior approval of the authority will be required as to— (a) transport and highways impacts of the development, (b) contamination risks on the site, (c) flooding risks on the site, (d) impacts of noise from commercial premises on the intended occupiers of the development, and (e) the provision of adequate natural light in all habitable rooms of the dwellinghouses. and the provisions of paragraph W (prior approval) apply in relation to that application. (2) Development under Class O is permitted subject to the following conditions— (a) the development must be completed within a period of 3 years starting with the prior approval date; and (b) the developer must apply for a determination under sub-paragraph (1) on or before 31st July 2021”

38. “Paragraph W” referred to in Part O.2(1) above is paragraph W of Schedule 2 to the GPDO, and it states as follows: “Procedure for applications for prior approval under Part 3 W.—(1) The following provisions apply where under this Part a developer is required to make an application to a local planning authority for a determination as to whether the prior approval of the authority will be required. … 12) The development must be carried out— (a) where prior approval is required, in accordance with the details approved by the local planning authority; (b) where prior approval is not required, or where sub-paragraph (11)(c) applies, in accordance with the details provided in the application referred to in sub-paragraph (1) unless the local planning authority and the developer agree otherwise in writing”.

39. The approach to be adopted by the court when reviewing an inspector’s decision letter was summarised by Lindblom LJ in St Modwen Developments Limited v Secretary of State for Communities and Local Government [2018] PTSR 746 at [6]-[7] as follows: “6. In my judgment at first instance in Bloor Homes East Midlands Ltd. v Secretary of State for Communities and Local Government [2014] EWHC 754 (Admin) (at paragraph 19) I set out the ‘seven familiar principles’ that will guide the court in handling a challenge under section 288. This case, like many others now coming before the Planning Court and this court too, calls for those principles to be stated again – and reinforced. They are: ‘(1) Decisions of the Secretary of State and his inspectors in appeals against the refusal of planning permission are to be construed in a reasonably flexible way. Decision letters are written principally for parties who know what the issues between them are and what evidence and argument has been deployed on those issues. An inspector does not need to “rehearse every argument relating to each matter in every paragraph” (see the judgment of Forbes J. in Seddon Properties v Secretary of State for the Environment (1981) 42 P&CR 26, at p.28). (2) The reasons for an appeal decision must be intelligible and adequate, enabling one to understand why the appeal was decided as it was and what conclusions were reached on the ‘principal important controversial issues’. An inspector’s reasoning must not give rise to a substantial doubt as to whether he went wrong in law, for example by misunderstanding a relevant policy or by failing to reach a rational decision on relevant grounds. But the reasons need refer only to the main issues in the dispute, not to every material consideration (see the speech of Lord Brown of Eaton-under-Heywood in South Bucks District Council and another v Porter (No. 2) [2004] 1 WLR 1953 , at p.1964B-G). (3) The weight to be attached to any material consideration and all matters of planning judgment are within the exclusive jurisdiction of the decision-maker. They are not for the court. A local planning authority determining an application for planning permission is free, “provided that it does not lapse into Wednesbury irrationality” to give material considerations ‘whatever weight [it] thinks fit or no weight at all’ (see the speech of Lord Hoffmann in Tesco Stores Limited v Secretary of State for the Environment [1995] 1 WLR 759 , at p.780F-H). And, essentially for that reason, an application under section 288 of the 1990 Act does not afford an opportunity for a review of the planning merits of an inspector’s decision (see the judgment of Sullivan J., as he then was, in Newsmith v Secretary of State for Environment, Transport and the Regions [2001] EWHC Admin 74 , at paragraph 6). (4) Planning policies are not statutory or contractual provisions and should not be construed as if they were. The proper interpretation of planning policy is ultimately a matter of law for the court. The application of relevant policy is for the decision-maker. But statements of policy are to be interpreted objectively by the court in accordance with the language used and in its proper context. A failure properly to understand and apply relevant policy will constitute a failure to have regard to a material consideration, or will amount to having regard to an immaterial consideration (see the judgment of Lord Reed in Tesco Stores v Dundee City Council [2012] PTSR 983 , at paragraphs 17 to 22). (5) When it is suggested that an inspector has failed to grasp a relevant policy one must look at what he thought the important planning issues were and decide whether it appears from the way he dealt with them that he must have misunderstood the policy in question (see the judgment of Hoffmann L.J., as he then was, South Somerset District Council v The Secretary of State for the Environment (1993) 66 P&CR 80, at p.83E-H). (6) Because it is reasonable to assume that national planning policy is familiar to the Secretary of State and his inspectors, the fact that a particular policy is not mentioned in the decision letter does not necessarily mean that it has been ignored (see, for example, the judgment of Lang J. in Sea Land Power & Energy Limited v Secretary of State for Communities and Local Government [2012] EWHC 1419 (QB) , at paragraph 58).’ …

7. Both the Supreme Court and the Court of Appeal have, in recent cases, emphasised the limits to the court's role in construing planning policy (see the judgment of Lord Carnwath in Suffolk Coastal District Council v Hopkins Homes Ltd [2017] UKSC 37 , at paragraphs 22 to 26, and my judgment in Mansell v Tonbridge and Malling Borough Council [2017] EWCA Civ 1314 , at paragraph 41). More broadly, though in the same vein, this court has cautioned against the dangers of excessive legalism infecting the planning system – a warning I think we must now repeat in this appeal (see my judgment in Barwood Strategic Land II LLP v East Staffordshire Borough Council [2017] EWCA Civ 893 , at paragraph 50). There is no place in challenges to planning decisions for the kind of hypercritical scrutiny that this court has always rejected – whether of decision letters of the Secretary of State and his inspectors or of planning officers’ reports to committee. The conclusions in an inspector's report or decision letter, or in an officer's report, should not be laboriously dissected in an effort to find fault (see my judgment in Mansell , at paragraphs 41 and 42, and the judgment of the Chancellor of the High Court, at paragraph 63).”

40. I turn now to consider the submissions of the parties in relation to the grounds that have permission to be pursued. Ground 1(a) – interpretation of section 55 of the 1990 Act Appellant’s submissions

41. For the Appellant, Ms Jackson submitted that the Inspector wrongly interpreted the relevant provisions of section 55 of the 1990 Act, leading ultimately to an error in his conclusion that the works undertaken to the Building were unlawful at the time when the material change of use took place.

42. There are several elements which together form this overarching submission.

43. Firstly, the Inspector misunderstood the relationship between sections 55(1), 55(1A) and 55(2) of the 1990 Act. Section 55(1A) lists a series of activities (defined as “building operations”) which are expressly included in the broad definition of “development” for the purposes of section 55(1). By contrast, section 55(2) lists a series of building operations which are nevertheless excluded from the definition of “development”.

44. Secondly, amongst the section 55(2) exclusions are works of “maintenance, improvement or other alteration” which “(i) affect only the interior of the building or (ii) do not materially affect the external appearance of the building” (per section 55(2)(a)). In this regard, Ms Jackson submitted that case-law interpreting section 55 has established two things of particular relevance to the facts of this case: i) that works of “maintenance, improvement or other alteration” can be extensive but they will still not encroach beyond the definition unless the product is something that is no longer the same building. This is a question of fact and degree. (For both propositions see Hewlett v Secretary of State for the Environment [1985] JPL 40, Court of Appeal). Ms Jackson noted it was common ground in the appeal both that the works were works of “improvement” and that the resultant building did not constitute a new building, and ii) the materiality of an effect on external appearance is context-specific, and works that are material in one location may not be material in another ( Burroughs Day v Bristol City Council [1996] 1 PLR 78). Ms Jackson submitted that the Inspector had failed to grapple with these concepts in reaching his decision that the works undertaken to the Building constituted “development”.

45. Thirdly, Ms Jackson submitted that the Inspector had failed to consider whether the works undertaken to the Building – even if they constituted “development” – were nevertheless undertaken pursuant to a planning permission. In undertaking works pursuant to a planning permission, even a material deviation from plans approved as part of that planning permission did not render all of the works unlawful. The materiality of the departure from approved plans is a question of fact and degree ( Hillside Parks Limited v Snowdonia National Park Authority [2022] UKSC 30 ). Ms Jackson submitted that the only works undertaken to the Building which both affected the external appearance and represented a departure from the 2017 Permission were the changes to the front and rear fenestrations and the lift shaft overrun, and that these were not material. SoS’s submissions

46. For the Secretary of State, Mr Forrest submitted firstly that the Appellant’s criticisms of the Inspector proceed from an unduly narrow and forensic reading of what the DL says. He submitted that, properly construed, the Inspector understood perfectly well the correct relationship between sections 55(1), (1A) and (2) and that his reasoning reflected that relationship.

47. As to the allegation that, on the facts, the Inspector should have concluded that the works to the Building fell within the section 55(2)(a) definition of works for “the maintenance, improvement or other alteration” of the Building, Mr Forrest responded that the words of the statute have been chosen deliberately to allow for the exercise of planning judgement, in what will prove to be circumstances with infinitely variable facts. No single test applies to the interpretation of the phrase. The court’s reasoning in other cases relied upon by the Appellant – for example Hewlett – were context-specific and obiter, or else not on point at all. Moreover, the Inspector’s conclusion in DL22 that the works “went beyond mere repair and/or alteration [and] [t]hey were substantial and extensive works of rebuilding” cannot be assailed on the facts.

48. Properly construed, the Inspector made a finding that section 55(2)(a) was not engaged. It follows, submitted Mr Forrest, that he was not required to make any findings in relation to the criteria in sub-paragraphs (i) and (ii) of section 55(2)(a) because they were immaterial to his decision.

49. Mr Forrest added that there is no reasons challenge levelled against the Inspector’s decision, but in any event the reasons were clear and adequate. They also reveal that even if the Inspector had considered the criteria in section 55(2)(a)(i) and (ii) his decision would inevitably have been the same, and hence even if the court found an error in the Inspector’s approach it should withhold any relief (per Simplex (GE) Holdings Ltd v Secretary of State for the Environment [2017] PTSR 1041 ).

50. Finally, so far as compliance with the 2017 Permission is concerned, Mr Forrest submitted that it was plain the Inspector was aware of the terms on which that permission had been granted. He had the material before him and he had undertaken a site visit. He was entitled to conclude, as he did, that what had been built was a material departure from the approved plans. There was no requirement for this conclusion to be rehearsed in any greater detail in the DL. Ground 2 – interpretation of the Prior Approval by reference to extrinsic material Claimant’s submissions

51. The Inspector was correct to note the agreed position between the parties that two plans referred to on the Prior Approval did not exist. However, the approach which the Inspector adopted to resolving what he therefore considered to be an ambiguity on the face of the decision notice was wrong in law.

52. Firstly, the Inspector was wrong to treat the floorplans as being incorporated into the Prior Approval. The decision notice referred to the application materials, but it did not go further in requiring (for example) that development must be carried out in compliance with them. Contrary to the Inspector’s comments in DL18, the fact that those details “were considered by the Council” in its decision to grant the Prior Approval is irrelevant in the absence of suitable incorporation wording on the face of the decision notice itself.

53. Secondly, there was in fact no ambiguity. The decision notice made clear that it was approving a material change of use from office use to residential use. Properly construed, the decision notice – although referring to the plans which accompanied the application for the Prior Approval – did not require that the change of use take place only in accordance with those plans. A change of use to twelve residential units is what was permitted, purely and simply, and this is what happened. There was therefore no ambiguity.

54. Thirdly, the fact that the Appellant might have understood himself to be tied to the application plans (per the comments in DL17 seen in the extract above) was neither “pertinent” nor legally relevant. Neither the subjective understanding of the Appellant nor of the Council can guide the objective interpretation of the Prior Approval.

55. Fourthly, if there was an ambiguity to be resolved then it was not resolved by looking just at these application plans. The extrinsic material forming part of the application for prior approval included other plans related to the assessment of highways impact which differ from other application plans, and although those plans were referred to expressly in the delegated report of the Council’s officer they are not referred to at all on the Prior Approval decision notice. The Inspector’s reference to extrinsic material in the form of the application plans is therefore incomplete, and it serves to further confuse the issue rather than clarify it.

56. As such, there was in fact no requirement for the Appellant to try and agree with the Council amendments to the details approved by the Prior Approval pursuant to paragraph W(12). The only “details” that were approved by the Prior Approval were the fact that the material change of use was for the creation of twelve residential units. That is what occurred. Reference to the plans on the Prior Approval was superfluous. SoS’s submissions

57. For the SoS, Mr Forrest submitted that the key question was whether, properly interpreted, the plans submitted with the application for the Prior Approval were incorporated into the Prior Approval decision itself. In this instance the Prior Approval decision notice used the term “accompanied by plans or documents listed here:” before then reciting four plan references. Two of these are acknowledged not to exist. The other two (being plan PL/01-J showing the location of the block and some of the external layout such as car parking spaces and waste storage, and the location plan) do exist, and the former is in evidence before the court.

58. Mr Forrest submitted that the reference to the four plans does create an ambiguity, because two of them exist and the other two do not. In such circumstances the Inspector was entitled to have regard to extrinsic material to resolve the ambiguity, namely the full suite of application documents including all four correct plans. This brings into consideration the layout plan, being one of the two plans incorrectly referenced on the Prior Approval.

59. The parties agreed that the development had not been carried out in accordance with the layout plan. Mr Forrest submitted that, contrary to the Appellant’s position, this was a relevant factor. Moreover, the Inspector’s conclusion at DL15 was that “On any comparison of the approved and as-built details, the changes are plainly evident and substantial”. This was the Inspector’s emphatic rejection of the argument advanced for the Appellant, which he recorded earlier in DL15, as being that “the actual departure from the approved details is not significant and can be described as ‘trifling’”.

60. Responding to the Appellant’s first submission, Mr Forrest submitted that the plans must be complied with if they have been “approved” by the Council through the decision notice – per paragraph W(12)(a). In this case they had.

61. As to the Appellant’s second submission, Mr Forrest responded that the Prior Approval decision notice could not be said to have approved details confined to just the description of the change of use. Two of the plans referred to in the Prior Approval are in existence. The fact that the other two are not creates an ambiguity which the Inspector was entitled to seek to resolve, and he did this by referring to the actual plans that were submitted with the application for the Prior Approval and treating them all as being properly incorporated into the decision.

62. Mr Forrest’s response to the Appellant’s third submission was that the Inspector’s conclusions did not rely on the fact that the parties had assumed all the plans from the application were incorporated into the decision. He was merely observing what the Appellant and the Council appeared to have believed, but his core conclusion was based on his interpretation of the decision notice, assisted by his reference to extrinsic material, not the subjective belief of the parties.

63. Finally, the additional plans in the highways assessment to which the Appellant now referred were apparently not brought to the attention of the Inspector as part of the enforcement notice appeal. This much can be discerned from the Appellant’s written closing submissions to the Inspector. As such, the argument now advanced cannot be used to impugn the Inspector’s reasoning in his DL. In any event, submitted Mr Forrest, even a reference to those extra plans does not answer the fact that it was permissible to have regard to two plans that were clearly part of the application for the Prior Approval and would have been referred to on the decision notice but for the administrative error in recording the wrong reference numbers. Costs decision Appellant’s submissions

64. The appeal against the costs decision is based on the argument that the Inspector wrongly concluded that permitted development rights for the change of use had been removed. Had he concluded otherwise, it follows that the appeal in its entirety was unnecessary and therefore the Appellant should have been awarded its costs for the entire appeal. SoS’s submissions

65. Mr Forrest relied upon his submissions in relation to Ground 1(a) in the substantive appeal, and submitted that if that appeal fails then so must the appeal against the costs decision. Discussion and conclusions Ground 1(a)

66. Criticism is levelled at the way the Inspector applied the elements of section 55 of the 1990 Act, and in particular how he approached the relationship between the different sub-sections. Ms Jackson for the Appellant submitted that this caused the Inspector to fall into error.

67. It is appropriate to set out how I consider the exercise should be approached here, and to then compare it with how the Inspector approached it.

68. The essential elements of a decision-maker’s thought process on section 55 should be as follows, by reference to the particular statutory provisions: i) Have there been activities carried out on the site which constitute “development”? ii) Relevant to the facts of Ground 1(a), “development” as defined in section 55(1) includes “the carrying out of building … operations” iii) Section 55(1A) then sets out a series of activities which are expressly in cluded within the definition of “building operations”. Amongst other they comprise (section 55(1A)(b)-(d)) “(b) rebuilding; (c) structural alterations of or additions to buildings; and (d) other operations normally undertaken by a person carrying on business as a builder”. At first blush, therefore, the works undertaken to the Building do fall within the definition of “building operations”; iv) However one must then consider section 55(2), which expressly ex cludes from the definition of “development” (whether as “building operations” or any other form of development falling within section 55(1)) a series of different types of activity. Amongst them are works for “the carrying out for the maintenance, improvement or other alteration of any building of works which – (i) affect only the interior of the building, or (ii) do not materially affect the external appearance of the building” (section 55(2)(a)); v) Section 55(2) trumps section 55(1A). That is to say, works which section 55(1A) specifically brings within the definition of a “building operation” – being a sub-set of the wider term “development” – will nevertheless still not constitute “development” if they satisfy the criteria in any of the sub-paragraphs of section 55(2); vi) The section 55(2)(a) exclusion involves two sets of criteria, both of which must be satisfied. The works in question must be both (i) building works carried out for the “maintenance, improvement or other alteration of any building”, and (ii) works which either affect only the interior of the building, or, if they affect the external appearance of the building, they do not do so materially; vii) Any works which are not thereby excluded from the definition of “development” require the grant of planning permission (section 57); viii) Such works may already benefit from the grant of an existing planning permission; ix) If not benefiting from an existing planning permission the works may nevertheless benefit from permitted development rights conferred by the GPDO, being a development order enacted pursuant to section 59; x) In considering whether available permitted development rights authorise the works in question it is necessary to consider (a) whether the works fall within the relevant description for that Class of development within the GPDO and are not specifically excluded, (b) whether any conditions attaching to the planning permission deemed to be granted by the GPDO have been complied with, and (c) whether permitted development rights have been removed in the case of the particular property, for example by a condition imposed on an earlier grant of planning permission that has been implemented or by operation of a direction made under article 4 of the GPDO

69. Not every one of the above considerations fall to be assessed on the facts of this case, but several do. They are as follows. Are the works carried out “for the maintenance, improvement or other alteration” of the building?

70. I was referred by the parties to several authorities in relation to this question. Chief amongst them was Hewlett v Secretary of State for the Environment [1985] JPL 404, a decision of the Court of Appeal. That case considered provisions of section 22 of the Town and Country Planning Act 1971 , being the predecessor to the 1990 Act, but it suffices to note that the substance of section 22(2) (a) of the 1971 is the same as that of section 55(2)(a) of the 1990 Act.

71. Hewlett also involved an appeal against an enforcement notice decision. The notice had been served on the owner in connection with works he had undertaken to a commercial building. The works were described in the judgment as “jacking up the roof, then undertaking certain operations to the walls in turn, and then at a later stage probably working on the roof itself”. The case for the appellant in front of the appeal Inspector had been that the works in question were “merely improvements” and did not materially affect the external appearance of the building.

72. The appeal was dismissed in the High Court. On appeal to the Court of Appeal, Sir John Donaldson MR, giving the leading judgment, considered the range of potential outcomes in cases of this nature. He held, at page 405: “The inspector had four possible conclusions available to him. The first was that there never had been a building here at all, so there could be no question of improvement. The second was that whilst there had been a building, all these works could reasonably be regarded as coming within section 22(2) (a) as being “maintenance, improvement or other alteration” of that building not materially affecting the external appearance. The third was that the external appearance had been materially altered. The fourth was that the work of maintenance, improvement or alteration had reached the point at which the previous building had been improved out of existence and had become a new building”

73. Ms Jackson submitted that the four possible outcomes identified by the Master of the Rolls fell into two categories. The first and second outcomes would not pose a problem for an appellant, but the third and fourth would.

74. I was also referred to the case of Arnold v Secretary of State for Communities and Local Government [2015] EWHC 1197 (Admin) , in which Dove J had considered the boundaries of Hewlett outcomes three and four against the facts of the case presented to him. He held, at [64]-[66]: “64. … it has to be borne in mind that the question of whether what was in situ was a new building or a remodelled version of the existing dwelling was a question of fact for the Inspector …

65. The Appellants complain that the Inspector did not expressly explore whether the extent of the demolition works could be explained on the basis that they involved the exercise of implementing permitted development rights and were themselves justified by the extent of repair necessary to the building.

66. In my view, the complaint is unfounded for two reasons. Firstly, as an issue it is a matter which is in effect bound up in the question which the Inspector asked himself as to whether or not as a matter of fact he was concerned with the staged extensions to an existing dwelling which were arguably not development or alternatively, in truth, with the construction of a new building with the integration of a few remaining walls. He was entitled to conclude on the evidence before him that what had happened was the latter”

75. In the present case it was common ground that the product of the works was not an entirely new building. That must be right on the facts, it seems to me. The impact which the works had on the appearance of the building, and the extent to which any parts of the works were already authorised by the 2017 permission, are two separate questions to be considered. But on any sensible analysis the works are nowhere close to the territory of producing a wholly new building.

76. That is sufficient to remove from consideration in this case Hewlett outcome number four. But there is, on Ms Jackson’s characterisation, outcome three which may still pose a problem for the Appellant. That entails different considerations. Did the works materially affect the external appearance of the property?

77. As I set out above, to fall within the section 55(2) exemption it is not sufficient to conclude merely that the works constitute works of maintenance, improvement or other alteration. They must also constitute either (a) works which affect only the interior of the building (section 55(2)(a)(i)) or (b) works which do not materially affect the external appearance of the building (section 55(2)(a)(ii)).

78. In the context of assessing the materiality of a change to external appearance, both parties referred me to the case of Burroughs Day v Bristol City Council [1996] 1 PLR 78. In that case Richard Southwell QC (sitting as a Deputy High Court Judge) was asked to consider whether alterations to a building at roof level constituted development. A central question was whether, under section 55(2)(a) of the 1990 Act, the works materially affected the external appearance of the building. On the particular facts of that case there was a focus on whether works to the roof could be seen from normal vantage points (for example from the street or by overlooking from other adjacent buildings of a similar or greater height). The judgment of Mr Southwell QC included the following passages: “The words of s55 have to be interpreted generally, since they may apply to an infinite range of different buildings, including a Second World War pre-fabricated home about 8 feet high, houses of 2, 3 or more storeys, factories, tower-blocks of flats, and office buildings of one to perhaps a hundred storeys … … The external appearance must be “materially” affected. This involves a judgement as to the degree to which the particular alteration affects the external appearance. The effect must be more than de minimis … Whether the effect of an alteration is “material” or not must in my judgement depend in part on the degree of visibility. A change to the front wall of a building or the front of the roof which is visible from the street is much more likely to be “material”, than a similar change which can be seen only from the top of much taller buildings. … In my judgement whether the external appearance of a building is “materially affected” is likely to depend on both the nature of the building and the nature of the alteration … “Materiality” must in every case take into account the nature of the particular building which it is proposed to alter. It is obvious that what is not a material alteration to the external appearance of a factory … may be a material alteration to the external appearance of an 18 th century house (whether or not it is listed or in a conservation area)”

79. For the Appellant in this case, Ms Jackson sought to align herself with two particular aspects from this extract. Firstly, that some of the works to the Building are at roof level and cannot easily be seen from vantage points on the ground (namely the lift shaft works), and, secondly, that the Building sits within an industrial estate which (Ms Jackson submits) is much less sensitive to changes to external appearance than a primarily residential area would be.

80. I consider the applicability of these two points when considering how the Inspector tackled the assessment of materiality. What can clearly be derived from Burroughs Day, though, are the propositions that (a) a change must be more than de minimis before it can be considered to be “material”; (b) materiality will be context-specific in every case; and (c) so long as the first two propositions are adhered to, the conclusion about materiality must be a matter for the planning judgement of the decision-maker. How far can the works in question be taken to be authorised by another actual or deemed planning permission?

81. As I have noted above, part of the case for the Appellant is that the works he undertook were at least partly in reliance on the 2017 Permission. Ms Jackson fairly conceded that not all of the works could be said to be so authorised, but she identified only two aspects of the works – the lift shaft overrun, and changes to the external fenestration – as being outwith the 2017 Permission.

82. Until relatively recently, undertaking works which involved a departure from the terms of a planning permission arguably rendered the whole of the works unlawful, even those parts that could be said to be wholly compatible with the permission. That was a consequence of the decision of the House of Lords in Sage v Secretary of State for the Environment, Transport and the Regions [2003] 1 WLR 983 , per Lord Hobhouse.

83. The position, however, has been clarified by the subsequent Supreme Court decision in Hillside Parks v Snowdonia National Park Authority [2022] UKSC 30 . In considering the case of Sage in their leading judgment in the case, Lord Sales and Lord Leggatt held as follows (at [60] and [63]): “60. In the course of his speech (with which the other law lords agreed) Lord Hobhouse referred to what he called the “holistic approach” of planning law and said, at para 23: “As counsel for Mr Sage accepted, if a building operation is not carried out … fully in accordance with the permission, the whole operation is unlawful. She contrasted that with a case where the building has been completed but is then altered or improved …” …

63. It is unclear exactly what counsel for Mr Sage accepted, as recorded by Lord Hobhouse in the passage quoted at para 60 above. If the concession was that, in carrying out a building operation, any deviation from the planning permission automatically renders everything unlawful, we doubt that this can be correct, even in relation to a single building”.

84. Thus, it is now tolerably clear that where (as here) development works partly comply and partly fail to comply with the terms of a planning permission, it is only the non-compliant works which can be said not to be authorised by the planning permission. What did the Inspector consider and conclude?

85. Against the above background I turn finally to review what the Inspector actually considered in this case, and the basis for his conclusion.

86. The key part of the decision letter relevant to Ground 1(a) is DL22. There the Inspector stated as follows: “It was put to me at the Inquiry that these works comprised repair and/or alteration, that some of the works affected only the interior, and those that affected the exterior did not materially affect the external appearance of the building. However, from the description of the works together with the visual extent of the works depicted in the photographs, I am of the view that the works that were undertaken to the building went beyond mere repair and/or alteration. They were substantial and extensive works of rebuilding and were structural alterations, which are sufficient to comprise building operations in their own right. As a result of this, I find that they do comprise development, and are not exclude from being so by Section 55(2) of the Act , as is contended by the appellant”

87. Against the various criticisms levelled by Ms Jackson I make the following observations.

88. As a matter of general approach the decision letter is to be read so as to accord with the “seven familiar principles” repeated by Lindblom LJ in St Modwen Developments Limited v Secretary of State for Communities and Local Government [2018] PTSR 746 . I have set out the relevant extract from St Modwen above. For present purposes I emphasise in particular the first of the seven principles, which bears repetition here: ‘(1) Decisions of the Secretary of State and his inspectors in appeals against the refusal of planning permission are to be construed in a reasonably flexible way. Decision letters are written principally for parties who know what the issues between them are and what evidence and argument has been deployed on those issues. An inspector does not need to “rehearse every argument relating to each matter in every paragraph”

89. Furthermore, for the reasons I have given above the extent of the unauthorised works needing to be assessed against the language of section 55 is confined to the fenestration changes and the lift shaft overrun works. All other aspects of the works form part of the 2017 Permission and were undertaken in compliance with it. Following Hillside , a departure from the scope of that permission for those parts of the works has no implications for the lawfulness of the other works.

90. I observe that the Inspector chose to characterise the works in this case as being works of “repair and/or alteration” whereas the submissions for the Claimant characterise them as works of “improvement”. I consider that nothing turns on this point. The statutory criteria in section 55(2) (a) apply equally to all types of works which are there described. Case-law guidance from, for example, Hewlett also draws no distinction between the assessments across the different descriptions of works found in section 55(2) (a) or its predecessor. I therefore see nothing untoward in the Inspector identifying the works as being “repair and/or alteration” rather than “improvement” regardless of how the parties before him had agreed to describe the works.

91. Howsoever they were described, Mr Forrest submitted to me that the works were incapable of satisfying the description of activities found in section 55(2) (a). On this basis he maintained that the Appellant’s Ground 1(a) “fell at the first hurdle”.

92. I cannot agree with that submission. Whilst accepting the common ground between the parties that the question of what constitutes works as described in section 55(2) (a) is a question of fact and degree, that there is no single test to be applied to the interpretation, and that facts which a decision-maker may be called upon to assess will be infinitely variable, I nevertheless derive considerable assistance from the observations of the Master of the Rolls in Hewlett and I am prepared to accept the four outcomes which he describes at page 405 as being apt for the exercise I must perform. Only one of those – outcome four – relates to works that are incapable of fitting within the description of “maintenance, improvement or other alteration”. I have concluded on the facts that an identification of the facts of this case with outcome four is wholly untenable.

93. Contrary to Mr Forrest’s urging, the Appellant does therefore clear the first hurdle comfortably.

94. But there is a second hurdle too. The works in question must not only fit within the description of works in section 55(2) (a), they must also not result in a material change to the external appearance of the Building. Is that hurdle cleared as well?

95. Ms Jackson’s criticisms of the Inspector’s approach note the absence of any reference to the effect of the works on external appearance. Instead, she submits, the error the Inspector made in the crucial DL22 is found in this passage: “I am of the view that the works that were undertaken to the building went beyond mere repair and/or alteration. They were substantial and extensive works of rebuilding and were structural alterations, which are sufficient to comprise building operations in their own right”.

96. This passage, submits Ms Jackson, illustrates that the Inspector fundamentally misunderstood and/or misapplied the relationship between sections 55(1) , (1A) and (2).

97. I do not agree.

98. In my judgement, a fair and benign reading of the decision letter (consistent with the guidance in St Modwen ) shows that, in substance, the Inspector did understand the interaction between the section 55 criteria correctly. In particular, I am content that the Inspector did consider both whether the works he referred to constituted works of maintenance, improvement or other alteration and whether they had a material effect on the external appearance of the building.

99. My conclusion here is based on two factors.

100. Firstly, DL22 – whilst a critical part of the Inspector’s conclusions – must not be read in isolation. In DL21, for example, the Inspector summarised accurately the criteria in section 55(2) , including the criterion regarding the works having a material effect on external appearance.

101. Secondly, in DL22 itself the Inspector acknowledged in terms the submission made to him at the inquiry by Ms Jackson for the Appellant. I have reproduced below DL22, with my own emphasis on the wording: “It was put to me at the Inquiry that these works comprised repair and/or alteration, that some of the works affected only the interior, and those that affected the exterior did not materially affect the external appearance of the building. However, from the description of the works together with the visual extent of the works depicted in the photographs, I am of the view that the works that were undertaken to the building went beyond mere repair and/or alteration. They were substantial and extensive works of rebuilding and were structural alterations, which are sufficient to comprise building operations in their own right. As a result of this, I find that they do comprise development, and are not exclude from being so by Section 55(2) of the Act , as is contended by the appellant”

102. The first part of the above extract from DL22 accurately summarises the position advanced for the Appellant in Ms Jackson’s closing submissions at the inquiry, which are in evidence before the court. When it comes to the Inspector’s reasoning, the fact that the first two parts of his summary are disconnected from one another, and from the third part, does not conceal the fact that his conclusions have been informed by an identification of both the correct statutory criteria (affecting the interior or not materially affecting the external appearance) and the evidence available to him from which to judge whether that criteria was met (photographs of the works, some of which showed the external works to the fenestration).

103. For completeness I record, and then respond to, the submissions made to me by Ms Jackson in which she sought to emphasise four things. Firstly, that nowhere in his reasoning at the end of DL22 does the Inspector acknowledge or rely upon the criterion of material effect on external appearance as a reason why the works do not fall within section 55(2) ; secondly, that his use of the words “as a result of this” appear to indicate that the Inspector concluded the works could not fit within section 55(2) simply because they were “substantial and extensive works of rebuilding” and/or “structural alterations” when in fact works which satisfied either or both of these descriptions could nevertheless still fall within section 55(2) ; thirdly, that the Inspector appears to have considered the cumulative effect of all the works that were undertaken to the Building without acknowledging that very few of them were works that did not already benefit from the grant of planning permission and which materially affected the external appearance; and fourthly, that had the Inspector acknowledged this last fact he would have recognised that the only unauthorised works which could materially affect the external appearance were the lift shaft overrun works (which could not really be seen from any external viewpoint) and the changes to the windows and fenestration (which, submitted Ms Jackson, represented a very small percentage of the works to the Building and which had many elements in common with what had been approved).

104. As to the first point, as I have shown in the extract above, whilst the criterion of material effect on external appearance did not appear in terms in the Inspector’s reasoning at the end of DL22, the early part of DL22 shows that he had the point firmly in mind.

105. As to the second point, I agree with the submission from Mr Forrest that to place reliance upon this form of words is to interpret the decision letter too forensically, as cautioned against by Lindblom LJ in St Modwen . The Inspector had made clear in DL22 itself that he was aware of the criterion related to a material effect on external appearance. One can easily infer from this his knowledge of its importance to an assessment against section 55(2) , and that his conclusion about the works falling outside of section 55(2) owes not merely to the nature of the works but to the nature of the works and to their effect on external appearance.

106. As to the third point, such a conclusion does not follow inevitably from the form of words used by the Inspector. In the early part of DL22 he summarised the submissions made for the Appellant at the inquiry that some of the works he could observe from the evidence should be discounted by him when assessing the extent of the works against the section 55(2) criteria. He was therefore aware of the Appellant’s case that not all of the works fell to be assessed for this purpose. The Inspector’s conclusions at the end of DL22 do not suggest a disagreement with that submission. Instead, they are perfectly consistent with a conclusion that, even taking into account only a smaller element of the works actually undertaken, they exceed what is necessary to fall within the section 55(2) exclusion because of their impact on external appearance.

107. As to the fourth point, I agree that if the lift shaft overrun cannot be seen easily from any external viewpoint it cannot rationally be considered to have a material effect on the external appearance. But the same is not true of the changes to the fenestration and windows. Ms Jackson invited me to consider the evidence of a comparison in sketch form of the changes to the fenestration from the works permitted by the 2017 Permission, and to the before-and-after photographs of the as-built works. She also noted the relatively small percentage of the building affected by works which were said to be unauthorised. But one must bear in mind that the Inspector’s conclusions about the materiality of the difference was an exercise of his planning judgement with which this court will not lightly interfere. Moreover, as Mr Forrest submitted, there are certain aspects of the decision in Burroughs Day which have been doubted subsequently. One example of this is, in my view, highly germane to the point under consideration here.

108. In Haringey London Borough Council v Secretary of State for Housing, Communities and Local Government [2020] P & CR 13, Lieven J had to consider a decision by an Inspector which included the assertion that “… the Burroughs Day judgment indicates that the change in external appearance also had to be judged in relation to the building as a whole, not by reference to a part of the building in isolation”. At [28] of her judgment, Lieven J commented as follows: “The first point to make is that in Burroughs Day the question of what was the building was not in issue, so the Inspector here does seem to have conflated the two matters. Secondly, however, to the degree that Mr Southwell QC was suggesting [in his judgment in Burroughs Day] that it is wrong as a matter of law to consider part of the building, in my view he was not correct. Mr Southwell QC did not refer to the fact that s.336 of [the 1990 Act] makes the definition of “the building” include “part of a building”. So, when s.55 requires consideration of the effect on the external appearance of the building, that can include part of the building. It is easy to imagine that in a large building, with different facades within public view, new fenestration might have a material effect on part of the building but not the whole. Given the statutory definition in s.336 it is open to the decision maker to take into account the impact on that part alone, and to the degree the judge in Burroughs Day was suggesting as a matter of law (rather than on the facts of the case) that was not material, in my view he was wrong”.

109. It follows from this analysis that submissions about what proportion of the building has been affected by unauthorised works is an unnecessary distraction. The point to be considered is: how material is the change to the appearance of such part of the building as has been changed? Viewed in that way as an exercise of planning judgement, it was perfectly rational for the Inspector to have concluded that the change to the fenestration and windows was material and sufficient of itself to remove the works from section 55(2) .

110. In my judgement, therefore, the Inspector did have the right test in mind.

111. If there is a criticism to be made of the Inspector it is from the fact that the disconnection in DL22 might appear to suggest that his incremental conclusions (“… they were …” and “… as a result of this …”) overlooked an essential element of the thought process. But as I have shown, read through no more than a reasonable and permissibly benign lens, they do not.

112. My conclusion that the Inspector did properly consider and apply the statutory tests means that it is unnecessary for me to consider Mr Forrest’s subsidiary submission based on the Simplex case.

113. For these reasons, Ground 1(a) fails. Ground 2

114. There is no dispute between the parties that there is an error on the face of the Prior Approval. Four plans are listed, two of which do not exist. No explanation has been advanced for how this error came to be made (although both parties speculate reasonably that it was a simple clerical error), or even what the erroneous plan references relate to. The core question in this case is whether the error makes any difference.

115. At the heart of Ms Jackson’s submissions is the fact that the Prior Approval did not include wording which required the change of use development to be undertaken only in accordance with the listed plans. On this basis, submitted Ms Jackson, there was no ambiguity needing to be investigated because the listing of the plans – correct or incorrect – was legally irrelevant.

116. As I note above, paragraph W(12) of the GPDO contemplates two different scenarios: i) Cases where a prior approval is determined to be required, but is granted by the local planning authority (paragraph W(12)(a)), and ii) Cases where prior approval is confirmed by the local planning authority not to be required (paragraph W(12)(b))

117. In the case of scenario (b), paragraph W(12)(b) provides specifically that development must be carried out in accordance with the details submitted as part of the application to ascertain the need for prior approval. But those are not the facts of this case. Had they been, it is clear that the list of drawings in the prior approval document (if any were listed at all) would indeed have been legally irrelevant, because what matters is ascertaining the plans submitted as part of the application. The irony is not lost on me that, in a case where prior approval were determined not even to be required, establishing the basis on which the development could then lawfully proceed would not have the same difficulties to overcome as those experienced in this case, because compliance is based unequivocally on the application details.

118. Reference was made by both parties to the judgment of Keene J (as he then was) in R v Ashford Borough Council, ex parte Shepway District Council [1999] PLCR 12. In that case, Keene J sought to summarise “the legal principles applicable to the use of other documents to construe a planning permission”, and at [19] he summarised five points, of which I emphasise points (3) and (4) as being especially relevant to the facts of this present case: “(3) For incorporation of the application in the permission to be achieved, more is required than a mere reference to the application on the face of the permission. While there is no magic formula, some words sufficient to inform a reasonable reader that the application forms part of the permission are needed, such as “… in accordance with the plans and application …” or “… on the terms of the application …”, and in either case those words appearing in the operative part of the permission dealing with the development and the terms in which permission is granted”. These words need to govern the description of the development permitted … (4) If there is an ambiguity in the wording of the permission, it is permissible to look at extrinsic material, including the application, to resolve that ambiguity”

119. This guidance has since been endorsed by high authority, for example the Supreme Court in Trump International Golf Club v Scottish Ministers [2015] UKSC 74 (per Lord Hodge at [33]). Ms Jackson relied additionally on the case of Polhill Garden Centre Limited v Secretary of State for the Environment, Transport and the Regions [1998] JPL 1017.

120. Those cases concern the grants of planning permission rather than prior approvals, but they consider what is on its face a similar question, namely what is required to incorporate application details into the authorising instrument and thereby to require compliance with them when carrying out the development.

121. In Polhill , planning permission was granted for a development comprising a retail store, warehouse and ancillary matters. The planning application form had included a box in which the applicant was asked to give a breakdown of the floorspace for the different elements. It had answered this question by stating that the area for the warehouse space would be 320 square metres, with 1,922 square metres for the retail space, and a total floorspace therefore of 2,242 square metres.

122. The permission was granted subject to a number of conditions, including one which required that, prior to construction, the applicant had to submit for approval details of the external finishes of the buildings. The details submitted by the applicant showed external finishes on a warehouse building that would be 704 square metres in size. The local authority refused the application, holding that the application revealed that a warehouse larger than that shown in the application form was intended to be built. The case for the local authority was that, although accepting there was no condition which specifically restricted the warehouse to 320 square metres in size, where it became apparent through the submission of other details that the developer intended to build something much larger than it had shown in the application this created an ambiguity for which it was permissible to rely upon the application details.

123. The court rejected the local authority’s argument. In his judgment Deputy High Court Judge Malcolm Spence QC stated, on page 1075: “I agree with Mr Dinkin that there is no ambiguity. Mr Mould’s real complaint is that there is no condition relating to the design of external appearance of the store (save for colour and texture of the materials), but in my judgment that is not an ambiguity. It has been trite law, especially in the early days following the inception of modern planning legislation in 1948, when reserved matters conditions were not imposed on permissions as commonly as nowadays, that if detailed drawings did not form part of the permission and the Planning Authority omitted to impose a reserved matters condition, the developer could construct the building in whatever dimensions and design he chose. Such a condition is normally imposed nowadays as a matter of form but that has not been done here in the case of the store, despite the fact that full drawings had been produced and permitted in respect of the remaining part of the permitted development”

124. Mr Forrest for the SoS referred me also to the case of Newark & Sherwood District Council v Secretary of State for Communities and Local Government [2013] EWHC 2162 (Admin) , a decision of Stephen Morris QC sitting as a Deputy High Court Judge. In that case an application had been made for a wind turbine designed to have two blades. Planning permission was granted on appeal, but the terms of the grant included a condition which required details to be submitted for a three-blade turbine. Mr Forrest relied in particular on [17] of the judgment, in which the Judge held: “… materials extraneous to the permission itself (including the application) can be referred where either (a) there are express words of incorporation in the permission (i.e. words in the operative part of the permission sufficient to inform a reasonable reader that the materials are part of the permission) or (b) there is ambiguity in the wording of the permission or a challenge on grounds of mistake: Ashford , supra, propositions (2) to (5)”

125. In my judgement, there is a distinction to be drawn between an error which renders a permission unintelligible and one which leaves the permission still intelligible even though the product may not be what either the applicant or the local planning authority intended. An example of the latter would be a permission referring to a list of drawings which includes some that are in existence but which were superseded by later drawings. That permission can still be understood on its face. It is not ambiguous. By contrast, the facts of the present case show it to be an example of the former. The Prior Approval refers to two plans which do not exist. Nobody can tell what they show or purported to show.

126. Polhill does not, in my view, extend the legal principles beyond those in Ashford and related cases upon which it relies. It serves merely as an illustration of how those principles are to be applied. In any event the ratio of Polhill , as expressed on page 1076 of the judgment, was that: “However, as I have already held, the floorspace box, is in any event not an aid to construction in the present case because there is no ambiguity on the face of the planning permission”

127. Newark & Sherwood is also no more than illustrative of how the guidance from Ashford et al. is to be applied. That the outcome was different from Polhill is explained by the fact that the internal interactions in the permission rendered it unintelligible. The permission had been granted for a two-blade turbine. The conditions required the submission of details to be for a three-blade turbine. That is a clear ambiguity. As was said by the Deputy Judge at [81] and [84-85]: “81. The issue here is whether, on its true construction, the Decision is a grant of planning permission for a two-bladed turbine, for a three-bladed turbine or for any wind turbine, regardless of number of blades. The real problem arising from Condition 5 is that, on its face, it prevents approval of a two-bladed turbine, and not merely that it permits approval of a three-bladed turbine. …

84. However, the permission itself is made expressly subject to the conditions, including Condition 5. Condition 5 not merely allows approval of a different make and model of turbine, but more significantly, requires the turbine to be approved to be a “three-bladed” turbine.

85. Thus, at this stage of the analysis, there is, within the terms of the permission granted at paragraph 1 of the Decision, not merely an ambiguity, but a clear inconsistency between the grant of permission for a two-bladed turbine and a condition of that permission requiring a three-bladed turbine and effectively prohibiting a two-bladed turbine. The Condition does not merely widen out the scope of type of turbine that can be approved beyond that which was the specific subject of the application. It fundamentally alters the type of turbine required”

128. Ms Jackson submits that even if the Prior Approval includes an ambiguity it is one that does not matter, because the two phantom plans appear in a list of documents which are not in any event to be read as being incorporated into the Prior Approval.

129. I do not agree. It is correct that the Prior Approval uses neither of the two formulations contemplated by Keene J in Ashford – “in accordance with” or “in the terms of” – nor anything similar to them. The wording which precedes the list of drawings on the Prior Approval is: “Prior approval for change of use from offices (Use Class B1(a)) to residential (Use Class C3) involving the creation of 12 x flats And accompanied by plans or documents listed here :” (my emphasis)

130. If one were construing a planning permission then I would agree with Ms Jackson that the SoS faces an uphill struggle in persuading me that the drawings were incorporated into the Prior Approval. But this case involves the interpretation of a prior approval under the GPDO, not the grant of a planning permission. In my view that distinction is significant, and I consider that it is sufficient to distinguish the case-law summarised above about reference to extrinsic materials as an aid to interpreting a planning permission.

131. What distinguishes prior approvals under the GPDO from planning permissions is the fact that the statutory code itself requires a consideration of the terms on which the prior approval is granted. This is the effect of paragraph W(12)(a).

132. The Prior Approval having been granted by the Council, the Inspector was obliged by paragraph W(12)(a) to consider the terms on which it was granted. In my view it cannot be correct, as Ms Jackson submitted, that the only term approved is a change of use producing twelve flats. That argument is wholly circular. “Change of use from offices … to residential … involving the creation of 12x flats” describes what has been approved, not the terms on which it has been approved. In order to discern those terms, reference must be made to the list of drawings which follow those words. And because that list of drawings includes an ambiguity, it is both necessary and permissible to have regard to the material submitted with the application.

133. In short, it is not the words of the Prior Approval itself which serve to incorporate the drawings, it is the requirement found in paragraph W(12)(a) of the GPDO. And once it is acknowledged that the incorporated drawings contain an ambiguity, then it is permissible to have regard to extrinsic details from the application.

134. I agree entirely with Ms Jackson that the details incorporated into the Prior Approval are not governed simply by what the parties thought they were. To that extent the Inspector would have been wrong in concluding that because the Appellant believed the application drawings to be incorporated (as evidenced by his several applications and concerted efforts to persuade the Council to change them) they must be taken to be incorporated. That said, I agree with Mr Forrest that the Inspector’s conclusions in DL17 were not based on that false assumption. The Inspector’s comments on that point are prefaced by the words “it is also pertinent to note …”. That certainly does not suggest to me that the Inspector relied at all for his conclusions on the actions of the parties, merely that he was noting the parties had in any event proceeded in accordance with what the Inspector had already assessed to be the correct legal interpretation of the Prior Approval.

135. My own conclusions on Ground 2 are similarly based on the statutory code, assisted in part by the case-law on reference to extrinsic materials in the grant of planning permission. But I am also reassured to observe that my conclusions do not result in any manifest injustice for the Appellant. The evidence shows that, prior to the appeal, the Appellant had assumed that his Prior Approval was granted on the terms he applied for. He made concerted attempts to have the Council agree to change them, invoking the procedure in paragraph W(12) to try and get the Council to do so. The Council’s refusal to cooperate resulted in a partial award of costs against it in the enforcement notice appeal. No party to the hearing claims that this partial award of costs was unjustified; the Appellant’s case is that the award of costs did not go far enough.

136. As DL16 records, it was not until “immediately prior to the Inquiry” that it was discovered two of the four drawings referred to on the Prior Approval did not exist. From that point onwards the submissions made on behalf of the Appellant, and repeated before the court, sought to profit from the newly discovered error by arguing that there was no need to vary the terms of the Prior Approval after all. Even if it were to be a relevant factor, the ultimate failure of this opportunistic argument does not result in any discernible injustice to the Appellant.

137. For the reasons given above I conclude that the Inspector was correct to approach the interpretation of the Prior Approval in the way he did. Ground 2 therefore fails. Costs decision

138. Both parties accepted that the challenge to the costs decision stands or falls by reference to the substantive challenge. As both grounds of challenge have failed, so too must the challenge to the costs decision.

139. For the avoidance of doubt, and for the reasons discussed above in relation to Ground 2, the partial award of costs which the Inspector did make in favour of the Appellant is left undisturbed. Conclusion

140. In light of my findings above it follows that the challenge to both the DL and the CDL are dismissed.

141. I now invite the parties to agree an appropriate form of order for my approval.