Two recent court rulings involving properties in Kensington and Chelsea highlight increasing scrutiny given to the housing supply backdrop on plans to amalgamate dwellings. (Royal Borough of Kensington and Chelsea v Secretary of State for Communities and Local Government; [2017] EWHC 1703 and 1704 (Admin))

The cases followed the same inspector’s decisions to allow proposals for amalgamation of four flats in Clarendon Road and two semi-detached cottages at Pembroke Cottages into single dwellings.

The High Court confirmed in R (Royal Borough of Kensington and Chelsea) v Secretary of State for Communities and Local Government, Reis and Tong [2016] that decision-makers are entitled to rely on their analysis of the effect of conversions on housing supply in determining whether to treat proposals for amalgamation as a material change of use and thus subject to planning control.

In these latest cases, the parties accepted that the inspector made a factual error in calculating housing land supply by deducting vacant units from the supply requirement but not from supply pipeline figures, thus overstating the pipeline. At Pembroke Cottages, this led him to conclude that there was additional "headroom" in the housing supply of 294 units over the requirement.

The council said the actual supply position was "very marginal", with a buffer of fewer than 20 units that would be eroded by amalgamations, and the figure could be even lower after an unrelated error. The appellants defended the decisions on the grounds that the error had not caused unfairness or been decisive.

The judge found it clear from the inspector’s reasoning that he had made a mathematical error, resulting in an overassessment of the housing supply. He held that the issue was whether the mistake had been material to the decision, not whether it had been decisive. He refused to exercise his discretion not to quash the decisions, on the basis that it was not possible to be sure that the inspector would necessarily have reached the same conclusion without the error.

The Clarendon Road decision letter noted that housing supply figures are thoroughly examined through the local plan process at a level of scrutiny that cannot be replicated while determining planning applications. That is obviously true, but these two decisions show there is likely to be an increasing level of interrogation of housing supply figures in such cases, particularly in central London boroughs with outdated amalgamation policies.

This article appeared in Planning Magazine, 8 September 2017