Newsnight | John Cairncross

Former KGB officer Oleg Gordievsky has identified the near-legendary 'fifth man' in the Cambridge spy ring as John Cairncross (pictured), a British intelligence officer during World War II. Though Cairncross is unavailable for comment, Gordievsky claims to have damning evidence that, along with Philby, Blunt, Burgess and Maclean, he passed secrets to the KGB for many years.

In his autobiography, 'The Enigma Spy', published in 1997 (two years after his death), John Cairncross denied both that he was the supposed 'fifth man' and that such a person had ever existed. Critics at the time viewed this book as a last attempt to clear his name, though few appear to have been convinced.