Janet Chisholm

Janet Chisholm, one of the most unlikely spies in the history of espionage, has died aged 75, without ever talking about her role in a major British cold war coup. In Moscow, as an officer in the British Secret Intelligence Service (MI6), she ran Oleg Penkovsky, a colonel in Soviet military intelligence (GRU), who passed Soviet secrets to the west at the time of the 1962 Cuban missile crises.

Penkovsky had been trying to offer his services to the west for some years, blatantly buttonholing diplomats and businessmen at receptions and approaching tourists in the street. The CIA considered that he was a Soviet agent provocateur and warned its officers to have nothing to do with him. But the British decided to give him a trial. The problem was how to collect his material in Moscow without alerting the KGB's counter-espionage department.

With London's approval, Janet Chisholm, the wife of the embassy's "visa officer", Ruari Chisholm, was assigned the job. She would take her young children for a walk in a park. Penkovsky would wander by, stop to admire the youngest child and slip a box of sweets into its pram. The box contained film of secret Soviet papers that Penkovsky had copied with his Minox camera.The idea was that anyone watching would assume it was an innocent, chance encounter between a matronly-looking foreign woman and an avuncular Russian man.

What no one in the west realised until too late was that the KGB already knew that the job of "visa officer", held by Janet Chisholm's husband, was just a front and that he was actually MI6's head of station in Moscow. The KGB knew this because Ruari Chisholm's previous posting was in MI6's Berlin station, where one of his fellow MI6 officers was George Blake, who had already secretly gone over to the KGB. Blake later admitted that he had given the KGB the names of every MI6 officer he knew.

So not only Ruari Chisholm but his wife was also under intense KGB surveillance from the moment they arrived in Moscow. Every time Mrs Chisholm left the embassy she was followed and photographed. It did not take the KGB long to identify the avuncular Russian who met Mrs Chisholm and her children as Penkovsky.

But the KGB did not act immediately. It had to consider the possibility that the GRU was trying to recruit Janet Chisholm or that there was some other reason why Penkovsky was meeting her. Any hasty KGB move might wreck an operation by a sister intelligence service and then there would be hell to pay. But a KGB search of Penkovsky's apartment when he was out revealed his cache of spying equipment and incriminating papers. He was arrested, and the Chisholms had to use their diplomatic status to leave the Soviet Union quickly. After a show trial at which Penkovsky confessed, he was found guilty of treason and shot.

Aspects of the Penkovsky affair remain controversial. Blake's confession that he had revealed to the KGB that the Chisholms were MI6 officers came in the middle of the Penkovsky operation. Therefore, MI6 had to accept that the KGB were on to Penkovsky because of his meetings with Janet Chisholm. Yet, instead of warning Penkovsky, MI6 allowed the meetings to continue. The then chief of MI6, Sir Dick White, said later that Penkovsky's determination to continue his work and the value of the information he was providing justified leaving him in danger.

But the value of Penkovsky's information has since been disputed. Although at the time every morsel was seized on by western intelligence experts, they now find it difficult to identify any single piece of military information that Penkovsky brought which proved to be of major value. One theory is that Penkovsky wrote his message in broad brush strokes. It dealt with capabilities and intentions. President John Kennedy read it and understood. Both he and the Soviet leader Nikita Khrushchev were educated into the realities of the nuclear age.

Janet Anne Deane was one of four daughters of a Royal Engineers officer, born at Kasuali in the foothills of the Himalayas. She was educated at Queen Anne's school, Caversham, where she learnt Russian. She studied French at Grenoble university and attended a secretarial school in London before joining MI6 at the Allied Control Commission in West Germany, where she met her future husband.

After Moscow, the Chisholms were posted to Singapore and then had two spells in South Africa. Ruari decided to take early retirement from MI6 and become an author. But he contracted cerebral malaria in Tanzania and died in Scotland a few weeks later.

Janet Chisholm continued a life of adventure, and in her 70s went backpacking around Australia and trekking in Tibet. But she never really abandoned the secret world and declined to talk or write about the Penkovsky case and her role in it, despite many attractive offers to do so.

She is survived by two sons and two daughters.

· Janet Anne Chisholm, born May 7 1929; died July 23 2004

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