He told the Standard: “They were just trying to put spanners in the works. It’s like ‘computer says no’.

Politically, someone somewhere has decided they just don’t like the development and they want to stop it. It’s so frustrating when we’ve been sitting on this site for a year and then they pull this out of the hat when there is absolutely no evidence.”

David Davidson, architectural adviser to the Hampstead Garden Suburb Trust, who was consulted by the council, said he was “absolutely convinced” that Oak Lodge is the work of the Scottish-born architect.

He said: ”There are 338 homes in the suburb and I know them all. I recognise the stylistic detail when I see it and I saw it at Oak Lodge. I would be very surprised if it turned out to be by someone else.”

Mr O’Brien plans to build a mansion with 18 two-to-five-bedroom apartments. His firm hired planning consultancy Turley Heritage to assess the architecture of Oak Lodge, which is locally listed as a “building of local architectural or historical interest”. However, English Heritage said it would not object to demolition when a previous planning application was lodged in the 1990s.

The proposed block would have a gym, swimming pool and spa and underground car parking, and retain an existing tennis court on the site.

A spokesman for Barnet council said: “All planning applications are considered impartially and on their individual merits.” A final decision is yet to be made by the planning committee.