Nabarro Nathanson senior partner David Bramson has put his name to a letter to The Times from senior London businessmen calling for a “£1.2bn investment backlog” in the London Underground to be made good by government.

Nabarros joined the London First campaign – a privately funded group of businesses to promote the city – two years ago.

Nabarros spokesman Chris Hinze said: “We have 800-900 people at Green Park. The Underground is invaluable to us.”