Royal Borough of Kensington And Chelsea v Secretary of State for Communities And Local Government

Under Class A of Part 1 of Schedule 2 to the Town and Country Planning (General Permitted Development) Order 1995, the “enlarged part” means the development carried out under the Order, not the whole dwelling house as enlarged. A single-storey basement remains a single-storey enlarged part, whether constructed above or below ground. The relevant seven-metre limitation is measured from the rear wall of the application dwelling house to the boundary of its own curtilage. Technical guidance cannot alter the ordinary statutory meaning. Where an inspector’s reasoning contains an error but the lawful development certificate was inevitable on the remaining findings, relief may be refused. An inspector may also treat an authority’s unexplained and insufficiently scrutinised change of planning interpretation as unreasonable behaviour for costs purposes.

Three claims concerned basement excavations beneath residential properties. Two claims under section 288 of the Town and Country Planning Act challenged inspectors’ decisions granting lawful development certificates for single-storey basements. The third claim sought judicial review of a costs decision arising from one appeal.

The central issues were whether “the enlarged part of the dwelling house” referred to the original dwelling house as enlarged or only the new development, how the seven-metre boundary restriction operated, whether any errors were material, and whether the costs decision was lawful.

1. Statutory construction. The wording of Class A distinguished “the enlarged part of the dwelling house” from the “original dwelling house”. The former meant the development permitted under the Town and Country Planning (General Permitted Development) Order 1995; the latter was the pre-existing building defined by article 1. The two components could combine to form the dwelling house as enlarged, but they were not the same thing.

2. The restriction concerning a dwelling house having more than one storey therefore applied to the new enlarged part alone. Each successive incremental development was to be assessed against the original dwelling house, so the interpretation did not permit impermissible “piggybacking”. A single-storey basement was a single-storey enlarged part. No distinction was required between storeys above and below ground. The subsequent limitations in paragraph A.1(f)(i) and (ii) were consequently not engaged in either appeal.

3. The seven-metre reference in paragraph A.1(f)(ii) concerned the distance from the rear wall of the application dwelling house to the boundary of the curtilage of that same dwelling house. It did not refer to the boundary of a separate dwelling house opposite. The explanatory material accompanying the 2008 amendment supported that construction, while technical guidance was not statutory and was wrong insofar as it required measurement by reference to the opposite house.

4. Although the inspectors’ reasoning on the seven-metre issue was erroneous, the delegated reports recorded that the other relevant Class A conditions were satisfied. The certificates were therefore inevitable. Applying the principles in Simplex GE (Holdings) v Secretary of State for the Environment and R (Smith) v North East Derbyshire PCT, the errors were immaterial and the section 288 claims were dismissed.

5. The challenge to the costs decision was also dismissed. The inspector gave adequate reasons for finding unreasonable behaviour, including the authority’s unilateral change of interpretation without consultation or wider scrutiny, its inconsistency with its former approach, and the absence of supporting legal authority or an appeal determination. All claims were dismissed. The claimant was ordered to pay the defendant’s costs, summarily assessed at £18,000.