One of the most spectacular defectors from Russia in terms of the “product” he brought with him when he came over in 1992, Vasili Mitrokhin first erupted into the public’s consciousness in September 1999 with the publication of his book The Mitrokhin Archive, written with Professor Christopher Andrew. Based on the unprecedented access he had had to KGB files through his work as the security organisation’s chief archivist from 1972 to 1984, this made a host of revelations about Soviet espionage and counter-espionage operations from the Bolshevik revolution of 1917 onwards.

Among the most fascinating of these was the revelation that an octogenarian grandmother, Melita Norwood, had been betraying British nuclear secrets to the Soviet Union for a period of 40 years from 1937. Such a disclosure led to a public furore which ended only with the Attorney-General of the day advising the Home Secretary, Jack Straw, that at such a distance a prosecution would be “inappropriate”.

Then there was the so-called “Romeo agent”, John Symonds, a detective sergeant in the Metropolitan Police, who, according to the archive, had fled the country when faced with corruption charges and had been recruited by the KGB in Morocco. After KGB “charm” training, his job thereafter was to seduce the employees of foreign embassies, with a view to obtaining secret information.

Among other revelations by Mitrokhin were plans to disrupt the 1969 investiture of the Prince of Wales, making it look like an MI5 plot to discredit Plaid Cymru, the Welsh nationalist party; a plot to injure and disfigure the defected Russian ballet dancers Rudolf Nureyev and Natalya Makarova, thus wrecking their careers; and details of hidden Soviet arms caches scattered throughout Western Europe and the US, to be used by agents and their pro-Soviet accomplices in the event of a war.

The Mitrokhin Archive also paraded a host of big American names, ranging from Henry Kissinger, whose phone calls to President Nixon the KGB claimed to have tapped, to Zbigniew Brzezinski, President Carter’s national security adviser, whom the KGB allegedly tried to recruit. At the other end of the scale were more spies, traitors and suspects: Robert Lipka, a clerk at the National Security Agency who spied for the Soviet Union in the 1960s and was jailed for 18 years; and Felix Bloch, the highest ranking State Department official ever to be investigated for espionage (he was sacked and stripped of his pension but the FBI never had enough evidence to charge him); as well as more detail about the familiar Burgess, Maclean and Philby.

It seemed an unprecedented treasure trove, as well as being a tremendous coup for British Intelligence. Mitrokhin had offered himself first to the CIA when leaving Russia via the Baltic States in the wake of the collapse of the Soviet Union. But the US agency was so overrun with defectors, each of whom had exotic claims to make about his or her fundamental importance to Western intelligence, that it turned him down. He therefore approached a British embassy, was welcomed with open arms and passed on to the Secret Intelligence Service (MI6) which brought him to London.

Sceptics nevertheless urged caution about the value of The Mitrokhin Archive. It was inevitably a heavily edited selection of Mitrokhin’s “six aluminium trunkfuls of notes” (some of which had been located by MI6 men after his departure from Moscow), worked on over a period of seven years. Some critics argued — the intelligence game being what it is — that the effect of the revelations was tendentious, that direct quotation was sparse, and that reference to specific documents was often absent.

Above all, the question was asked: what had led Mitrokhin to select and transcribe the particular documents he did — and what was he trying to prove? He had apparently become disillusioned with Communism in the early 1960s, when the changes promised by Khrushchev at the 20th party congress in 1956 had failed to materialise. Yet his defection, and the exposure of the evils of the Communist system, which he claimed as his goal, had had to wait for another 30 years, by which time that system had effectively ceased to exist — and had certainly ceased to be a threat to Western civilisation.

Nevertheless, The Mitrokhin Archive undoubtedly contained many vivid insights into the workings of the Soviet system, particularly at times when it came under pressures to which its ossified philosophy was not equal. Party reaction to the uncontrollable rumblings of the Solidarity period in Poland, for example, were vividly documented by the series of panic-stricken phone calls between the leadership and its servants in Warsaw.

Vasili Nikitich Mitrokhin was born in 1922 in Yurasovo in Ryazan oblast (province), the second of five children. His childhood was spent partly in Yurasovo and partly in Moscow, depending on where his father, a decorator, could find work and his large family could obtain food. This tended to mean that Mitrokhin spent most winters in Yurasovo, which imbued in him a deep love of the countryside.

After his secondary education, Mitrokhin entered an artillery school. With the German invasion of the Soviet Union in 1941 he moved to Kazakhstan, where he studied for a degree, graduating in law after first reading history. Towards the end of the war, Mitrokhin took his first job, in the military procurator’s office in Kharkov, Ukraine.

He then secured entry to the Higher Diplomatic Academy in Moscow, a three-year course, which ended with his recruitment in 1948 into the KI (Committee of Information), the name by which the Soviet external service was then known. In 1954 it was absorbed into the newly formed KGB (Committee of State Security).

Mitrokhin was shortly afterwards posted to the Middle East, an undercover assignment, which required extensive training and which lasted about three years until 1953. Back in the Moscow headquarters of the KGB, he was entrusted with operational work which involved occasional visits abroad under cover. In this capacity, he accompanied the Soviet team to the 1956 Olympic Games in Australia.