Ruth Werner, who died in her native Berlin on July 7th aged 93, was one of the Soviet Union's star agents. She was a member of the wartime Red Orchestra and Lucy spy rings in Switzerland before she came to Britain, where, using the codename Sonya, she was a courier for the atom spy, Klaus Fuchs.
She was born Ursula Kuczynski into a Polish Jewish family, supporters, like Fuchs, of the German communist party (the KPD). urgen, joined him in London in 1936, where despite - or, indeed, because of - his communist sympathies and anti-fascist credentials, he was later recruited by the OSS the - forerunner of the American CIA - to contact resistance groups in occupied Europe and draw up intelligence reports.
Ruth Werner's career as a spy began in 1930, when, with her first husband, Rudolf Hamburger, she went to live in Shanghai. Hamburger, an architect and Soviet agent, had taken a job with the British-administered Shanghai municipal council. She later described her shock at the poverty and exploitation in the city, where she soon became involved in revolutionary and communist circles.
She was approached by the German communist Richard Sorge, then the Soviet Union's master spy in the Far East (he was executed by the Japanese in 1944). She later described it as the "one event which was to prove decisive for my future life". Sorge, who gave her the codename Sonya, suggested she should go to Moscow for training in espionage and radio communications at the headquarters of the Red Army's intelligence service, the GRU.
She travelled extensively as a GRU agent, returning to China, where she helped to organise revolutionary forces fighting the Japanese along the Manchurian border.
In 1938, after settling her children in England, Werner was sent to Switzerland, the centre for Europe's espionage networks, including the Rote Kapelle (Red Orchestra) and the Lucy Ring, which was later used by Britain to pass intelligence about Germany to the Soviet Union. There she met Allan Foote, a British member of the Lucy Ring, who introduced her to a fellow veteran of the International Brigade in Spain, Len Beurton, whom she married in 1940.
The marriage entitled her to a British passport, and, after coming close to being denounced as a Soviet spy, she made her way to England, with Beurton following soon afterwards.
The family rented a cottage in Summertown, north Oxford, before moving to a large house in a nearby village - a convenient place from which Werner could handle Fuchs, then living and working in Birmingham - and at the atomic research centre at Harwell.
In 1942, Fuchs contacted Jurgen, whom he had known from their past communist days, and Jurgen immediately put him in touch with Ruth Werner. They had a series of meetings in Banbury, after which Werner passed Fuchs's information either to her Soviet controllers in London or directly to Moscow by radio.
In 1946, Moscow suddenly broke off contact with her for reasons that remain unexplained. However, it seems clear that, by the following year, her cover - and Beurton's - had been blown by Foote, because she was visited by two special branch officers. They appeared to have no evidence about what she had been up to, and, as she put it later: "They left us calmly and politely, but empty-handed." MI5 did not put her under surveillance either before or after the visits - the consequence of both incompetence and complacency.
She was allowed to leave Britain early in 1950 and went to East Germany, on the day before Fuchs was put on trial for giving away the west's atom secrets.
She was married three times, and had three children.
Ruth Werner: born 1907; died, July 2000