Both the brandy and the lighting were unusually strong and it all took place in a restaurant close to the Bolshoi Theatre equipped with a large divan bed.
The official account of the gay "honey trap" set by the KGB in 1955 to blackmail a British naval attaché into revealing defence secrets for seven years is revealed for the first time today in government papers.
John Vassall, the son of an Anglican vicar who became a junior official in the British embassy in Moscow and subsequently one of the KGB's most useful Cold War spies, was photographed taking part in a gay orgy after he was befriended by a Soviet agent working inside the diplomatic mission as a young man.
In return for regular payments, the naval clerk, whose codename was Miss Mary, then passed a succession of classified papers to his KGB minders after he returned to London, including details of British torpedoes and anti-submarine devices, until he was finally arrested at his Westminster flat in September 1962.
In a statement provided to Special Branch after officers raided his flat in Dolphin Square, the exclusive Thameside apartment complex favoured by politicians and for several years Princess Anne, Vassall explained how he had become friends with a Russian interpreter, Sigmund Mikhailsky, shortly after he arrived in Moscow in 1954.
After three months, Mikhailsky, who was a KGB plant, one night introduced Vassall, then aged 30, to a group of male friends who invited the Briton to join them for dinner in a private room at a restaurant two streets from the Bolshoi Theatre.
Vassall said: "We had drinks, a large dinner and I was plied with very strong brandy and after half an hour I remember everybody taking off their jackets and somebody assisted me to take off mine. In one corner there was a large divan.
"I remember the lighting was very strong and gradually most of my clothes were removed. I remember two or three people getting on to the bed with me, all in a state of undress. Then certain compromising sexual actions took place. I remember someone in the party taking photographs."
The documents released at the National Archives in Kew, west London, come from Vassall's Old Bailey trial, which was partly heard behind closed doors to protect state secrets.
Vassall was later approached by more KGB agents who threatened him with being stripped of his diplomatic immunity and put on trial for breaking Russian laws banning homosexuality. After giving into the Soviet blackmail, the civil servant led a double life while working at the Ministry of Defence as secretary to a junior minister, Thomas Galbraith, the son of a Scottish peer who eventually successfully sued for libel over claims that he was one of Vassall's lovers.
In return for his services, which were suspended in 1961 after the discovery of another Soviet spy ring in London, Vassall was paid by the KGB between £500 and £700 a year (equivalent to £8,000 to £10,000 today) in bundles of £5 notes.
The arrest of Vassall following a tip off to MI6 by Soviet defectors embarrassed the government and an inquiry was held into how he had managed to operate undetected for so long. The civil servant was sentenced to 18 years after pleaded guilty to espionage offences under the Official Secrets Act. He died in 1996.
For his part, Vassall, who insisted he had no Communist sympathies, told Special Branch that he regretted his actions but insisted he had been trying to avert conflict between the West and the Soviet bloc.
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