Controversial Basement Extension Threatened Diplomatic Incident

Basement extensions are increasingly popular, particularly in densely populated inner city areas with very high property prices, but they are by no means free from controversy. That was certainly so in one case in which plans to excavate under a listed building threatened to cause a diplomatic incident.

The house was once occupied by the Russian Soviet Mission but had been empty for some years. The couple who owned it under a long lease had been granted planning permission and listed building consent in 2008 to extend the property downwards by five stories, subsequently amended to three.

The French ambassador’s residence was next door and the French government had objected to the proposals, on grounds that it would interfere with the mission’s work. It pointed to the Vienna Convention on Diplomatic Relations, which imposes a special duty on signatories to take all appropriate steps to prevent any disturbance of the peace of diplomatic missions or impairment of their dignity.

In 2015, the local authority had granted the couple certificates under Section 192 of the Town and Country Planning Act 1990 and Section 26H of the Planning (Listed Buildings and Conservation Areas) Act 1990. They confirmed that the planning permission and the listed building consent had been lawfully implemented and could thus be lawfully completed. The French government’s challenge to those certificates was rejected by a judge.

In ruling on the dispute, the Court of Appeal could find no flaw in the decision that the planning permission had been implemented in 2011 when some internal excavation works were undertaken at the property. However, in allowing the French government’s appeal in part, the Court overturned the certificate granted under Section 26H on the basis that the council had applied the wrong legal test.

The council only had the power to issue the certificate if satisfied that the proposed extension would not affect the character of the house as a building of special architectural or historic interest. It had erred in applying the test for implementation applicable for determining a Section 192 certificate to the Section 26H certificate. The tests were different and the council had thus acted outside its powers.