Born into a family of good blood and little money, during the Second World War worked as a RAF photographer. John worked as a minor clerk in the Admiralty Office. In 1954, he became an assistant to the naval attaché at the British Embassy in Moscow.
John was homosexual and in 1955 a Soviet agent who had filmed him having sex with several men provided by the KGB. Thus KGB officers blackmailed him into being a spy. In Moscow he courted Sigmund Mikhailsky, a young man employed officially as an interpreter, and unofficially as the "fixer" at the embassy.
Every embassy had such a "fixer," who could cut through Soviet red tape, arrange theater and travel tickets, and, through the black market, obtain almost anything one might want. Mikhailsky was also attractive, amusing, and obliging about providing more personal services, heterosexual or homosexual.
After returning to London in 1956 John was assigned to the Admiralty's Naval Intelligence Division. Over the next few years Vassall provided the Soviets with thousands of highly classified documents on British naval policy and weapons development. After promotion in 1959 John was able to steal Admiralty secrets concerning radar, torpedoes and anti-submarine devices.
In December 1961, Anatoli Golitsin, a KGB agent, working in Finland, defected to the CIA. He was immediately flown to the United States and lodged in a safe house called Ashford Farm near Washington. Interviewed by James Angleton Golitsin supplied information about a large number of Soviet agents working in the West. He also provided information about two spies in the Admiralty. Using the information supplied by Golitsin, MI5 came to the conclusion that one of these men could be John Vassall.
Nikolai Karpekov, a diplomat working at the Soviet Embassy, warned John about Golitsin's defection and ordered him to cease operating until further orders. He also took away his camera that he had been using to photograph the secret documents.
In June 1962 Yuri Nosenko made contact with the CIA in Geneva. He was deputy chief of the Seventh Department of the KGB. His main responsibility was the recruitment of foreign spies. He like Golitsin, provided evidence that John was a Soviet agent. However, most of his evidence undermined that given by Golitsin.
Nikolai Karpekov now contacted John and gave him back the camera and ordered him to resume spying. On September 12, 1962, caught red-handed, John was arrested. He made a full confession. When he was arrested, John claimed he had attended a party given by Mikhailsky. The KGB provided handsome men and plenty of brandy.
Afterwards, he was shown photographs of himself enjoying a variety of sexual acts with several of the Russian men - in one photo posing between two very naked Russians, grinning and holding up their underwear like trophies.
Unless he became a spy, he said he had been told, he would be denied diplomatic immunity and prosecuted under Russia's draconian anti-homosexual laws. He began feeding British and NATO secrets to the Russians, who paid him generously.
In October, 1962, John was sentenced to 18 years' imprisonment. He was released in 1972. Vassall: The Autobiography of a Spy, was published in 1975.