Mr Steele first approached British intelligence at the £1.7million home of Sir Charles Farr, the chairman of the Joint Intelligence Committee, in Wimbledon, south-west London.

Mr Farr, who died in February at 59, was one of Mrs May‘s top counter-terrorism advisors at the Home Office.

After leading MI6‘s Russia desk, Mr Steele set up a private firm, and was hired by Fusion GPS, a US research company being paid by Hillary Clinton‘s campaign.