The facts
3.Barham House is a four-storey purpose-built block of eight flats which was constructed in 1938. It is located in the Molyneux Street conservation area to the east of Edgware Road in the London Borough of Westminster and sits in the middle of a terrace of 18th century houses which are all listed buildings. Barham House itself is not listed but it is mentioned in the conservation area policy as a building of merit. The terraced houses on either side are three-storey but Barham House is a four-storey building and rises above them. 4.Each of the terraced houses has a very small open lightwell at the front of the building from which light is admitted into a basement. The pavement at the front of Barham House abuts the face of the building and there is no lightwell and no basement, or at least no basement to which access is available.5.It is possible that Barham House was constructed on the foundations of two buildings which previously stood on the site and formed part of the terrace. If so, a void may exist beneath the ground floor of the current building where there was previously a basement. The terrace is shown in conservation area policy documents as having originally been continuous but the existence of a basement level below the modern building is a matter of speculation.6.There are two flats on each of the four floors of Barham House and all eight flats are let on long leases. On the ground floor a narrow communal hallway leads to a staircase to the upper floors and a door gives access to a small yard at the rear of the building. One of the ground floor flats has been extended at the rear into the yard.7.The freehold interest in the building was offered for sale at auction on 13 February 2020. The auction particulars described the lot as a freehold ground rent investment and suggested a guide price of £15,000 plus. The Tribunal was told that the vendor was a company in the Grainger Group, one of the UK’s largest residential property companies. 8.At the conclusion of the auction the appellant was the successful bidder at a price of £91,000.9.Almost immediately after the auction the respondent gave notice under section 13 of the 1993 Act on behalf of leaseholders of flats in the building that it intended to exercise the right to acquire the freehold. The notice was later said to be defective and a second notice was served on 10 June 2020. Both notices offered a premium of £18,000 for the freehold.10.The sale to the appellant was completed on 8 April 2020.11.On 11 May 2020 the appellant received pre-application planning advice from Westminster City Council. It had requested advice on the prospect of obtaining planning consent to excavate a single-storey basement to create a three-bedroom flat with associated light wells at the front and rear of the building, and to erect either a single-storey or a double-storey roof extension to provide either two three-bedroom flats or four one-bedroom flats. 12.In its advice the local planning authority recorded that only written advice had been sought and that no site visit had been made. It also referred to the fact that only limited information had been supplied with the pre-application enquiry and that floor plans which it had requested had not been provided. Barham House was described as making a positive contribution to the conservation area and the authority considered that the proposed roof extension would make it highly conspicuous and incongruous and would be detrimental to the character and appearance of the conservation area and harmful to the setting of the surrounding listed buildings. In short, there was no chance of planning permission being obtained for the proposed roof-top extension. 13.The basement excavation project faced fewer policy objections and the authority took the view that it would not harm the character or appearance of the conservation area. The acceptability of the proposed unit was nevertheless difficult to assess; one relevant consideration was whether it could receive enough natural light to form acceptable living accommodation. In principle, however a single basement level was likely to be considered acceptable subject to compliance with design standards.