THERE were many reasons why Yuri Nosenko found himself, in June 1962, sitting in an overstuffed armchair in a fussily furnished CIA flat in Geneva, with a glass of American whiskey in one hand and an American cigarette in the other, offering to sell “two pieces of information”. He suggested several of them himself. A prostitute had robbed him of his $250 spending allowance as a member of the Soviet disarmament delegation, and he desperately needed cash. He had spent too many nights on the town, and lost the money that way. Or it was not a matter of money at all; he simply wanted to get in touch with Americans, because the urge to defect to the West “was slowly growing in me since my studentship”.

But Mr Nosenko was no ordinary Russian. He was a member of the KGB, chief of the First Section of the Seventh Department of the Second Directorate, whose job was “work against tourists”. At that first meeting he declared himself not yet “psychologically ready” to defect. So for the next two years, with $25,000 deposited for him in a Western back account, he stayed in the KGB and passed on information. He had agreed that, on visits to the West, he would meet his contacts at 7.45pm outside the first cinema listed in the local telephone book two days after sending a telegram signed “George”. And so in February 1964 there he was, with his combed-back hair and broad, soulful face, loitering outside the ABC in Geneva as if waiting for a girl; but in fact eager, now, to jump.

The Oswald file

Over the previous two years, he had told his CIA contacts in detail how their chief informant, Popov, had been exposed; how bugs had been planted in the American embassy in Moscow; how the KGB had tried to recruit Americans and had laid honeytraps for others; and, most useful of all, how he had reviewed the entire KGB file on Lee Harvey Oswald, President Kennedy's killer, and knew for a fact that the KGB had never used him because he was “unstable”. This was riveting stuff. Perhaps, thought the high-ups in counter-intelligence in Langley, it was too good. It seemed to James Jesus Angleton, the head of CI, that Mr Nosenko was no random defector. He had been despatched by the KGB to call in question the information given by another source, Anatoly Golitsin, to divert his leads, to clear the Soviet Union of complicity in Kennedy's murder and (Angleton's wild head piling suspicion on suspicion) to work towards the destruction of the United States.

Mr Nosenko had his odd sides, undoubtedly. He seemed to have left his wife and daughters without compunction; they would be “OK”, he thought. He admitted he had made “stupid blunders”: drank too much, gone with too many women, invented fables about his life. He claimed to have twice run away to the front as a boy, itching to fight the Germans. He said he had graduated from the Moscow State Institute in 1949, concealing the fact that he had failed the Marxism paper and had to take his finals again. At his first Geneva interview he gave his KGB rank as lieutenant-colonel, when he had never got past captain. His father had been Stalin's minister of shipbuilding for 17 years, commemorated with a bronze plaque in the Kremlin wall. But the son was feckless, doing indifferently at his posh schools, recruited into the KGB only because Daddy knew General Kobulov and, at a party at the family's dacha in 1953, had introduced them.

His inflated KGB career had in fact been predictably modest, almost upended at the start when he showed his operative's papers and passport to a doctor treating him for gonorrhoea. That earned him arrest for 15 days. Between 1955 and 1963 he was shuffled around in various jobs within the Second Directorate. But his father's name still helped, earning him the privilege of trips abroad. While there, he decided he wanted to live in the West.

This simple motivation was not credited when he came to the United States. Instead, for three years, he was incarcerated and interrogated to make him confess that, first, he was not Nosenko and, second, that he had been sent on purpose. A small cell was built for him at a CIA facility in Maryland. The single window was boarded up, and a 60-watt bulb was kept burning. Weak tea and porridge were fed to him. He was not allowed to hear a sound or to read. When, in desperation, he secreted the instructions for a tube of toothpaste, they were taken away. When he made a calendar from threads unravelled from his clothes, it was destroyed. In one week, in 1966, he was given polygraph tests for 28½ hours. At one point an extra machine was fitted which could, he was told, read his mind. All this was later found to have contravened the CIA's founding charter. But it did not make Mr Nosenko change his story.

America's spies were as thoroughly divided about him as any KGB agent could have wished. In 1968, shamefacedly, the CIA rehabilitated him, awarded him $150,000 in compensation and gave him a new name. He settled somewhere in the South, unbitter and “well-adjusted”, married an American and was invited sometimes secretly to Langley to speak, to tumultuous ovations. And to friends in the agency he gave a new reason for that long-ago June day in Geneva. “I was snookered…I was drunk—very drunk.”