Upstairs Downstairs TV star John Alderton has lost his fight to block a neighbouring basement development in Hampstead.

A planning inspector overturned Camden Council’s ruling that plans to demolish and build a new larger house would have a negative impact on the actor’s historic home.

Mr Alderton, who has lived at the house with actor wife Pauline Collins for 33 years, claimed another basement in his already blighted road would wash away the foundations of his Grade II listed house.

In a letter to the planning inspector, the 71-year-old actor, who starred in Calendar Girls, said: “My shallow foundations are likely to be exposed to major damage. My house could become an island between two rivers.”

Planning inspector Olivia Spencer rejected the claims and said the chances of an underground damn forming were “very limited”. She also dismissed a report by a geologist at Imperial College London supporting Mr Alderton’s claims.

Building work on the basement development in the Redington and Frognal Conservative Area must begin within three years.