13. Cairncross admitted to spying in 1951 after MI5 found papers in Guy Burgess' apartment with a handwritten note from Cairncross. Some believe that he may have supplied information about the Manhattan Project, to assist the Soviet's quest for nuclear capability. The identity of the infamous 'fifth man' in the Cambridge Five remained a mystery outside intelligence circles until 1990, when KGB defector Oleg Gordievsky confirmed Cairncross involvment. Cairncross actually worked independently of the other Four and did not share their upper-middle class backgrounds or tastes. Although he knew Anthony Blunt at Cambridge and Guy Burgess in the Foreign Office, he claimed not to have been aware that they or any of the others were also selling secrets to the Russians. Between 1941 and 1945, Cairncross supplied the Soviets with 5,832 documents. In 1944, Cairncross joined MI6, the foreign intelligence service. Yuri Modin, the Russian KGB control in London claims that Cairncross gave him details of nuclear arms to be stationed with NATO in West Germany.