David Mellor memories of spy and Tory MP Raymond Mawby
28 June 2012 Last updated at 12:16 BST
Ray Mawby, a junior minister in Harold Macmillan's government in the 1960s and seen as a defender of right-wing traditional values, has been exposed as a spy for the former Communist Czechoslovakian secret service.
He is seen in a BBC TV programme claiming that gay people were more likely be a security risk - while he was already spying.
The BBC's Gordon Corera explains how he found out the MP spied for money while former Tory minister David Mellor shares his memories of Mr Mawby, who died in 1990.