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

A planning decision may be quashed where an inspector makes a mistake of fact which gives rise to unfairness. The mistake must concern an existing fact or objectively verifiable evidence, the claimant must not be responsible for it, and it must have played a material, though not necessarily decisive, part in the reasoning. In a challenge under section 288 of the Town and Country Planning Act 1990, the court reviews legality rather than planning merits. Decision letters are read flexibly, but the reasons must reveal how the principal controversial issues were resolved. Where a material numerical error affects the assessment of housing land supply and the court cannot be satisfied that the same decision would have been reached without it, the decision should be quashed.

The claimant local planning authority challenged under section 288 of the Town and Country Planning Act 1990 an inspector’s decision allowing an appeal against refusal of permission for the amalgamation of two dwellings into one. The authority alleged errors in the calculation of five-year housing land supply. It abandoned one ground, and the Secretary of State conceded the remaining ground concerning the treatment of vacant units returning to use. The second defendant argued that the error was immaterial because the inspector’s decision principally concerned the qualitative effect of losing one dwelling.

1. Application allowed. The inspector’s decision was quashed.
2. The court applied the established principles governing section 288 challenges. Decision letters must be construed flexibly, and the court must not reassess planning judgment. Nevertheless, the reasons must be intelligible and must address the principal important controversial issues.
3. A mistake of fact is a separate ground of challenge where it gives rise to unfairness. The relevant conditions are: a mistake about an existing fact or the availability of evidence; an objectively established and verifiable fact or matter; no responsibility on the claimant’s part for the mistake; and a material contribution by the mistake to the decision-maker’s reasoning.
4. The inspector had wrongly calculated the apparent housing supply headroom by deducting vacant units returning to use from the requirement while retaining them in the supply figure. The error was accepted, and the first three conditions were satisfied.
5. The error was material. The inspector described the extent of oversupply as significant, and that conclusion depended on the erroneous headroom figure. His conclusion that losing one dwelling would not significantly affect housing supply therefore had to be read in the context of the mistaken assessment.
6. The later discovery of a separate error in the authority’s monitoring report was relevant to discretion but had little bearing because it was discovered after the inspector’s decision. Since the court could not say that the inspector would have reached the same conclusion without the material error, it declined to withhold relief.