A modernist 1930s apartment building in London’s fashionable Hampstead was home to a spy network that gave away many of Britain’s nuclear secrets to Russia.
More than 20 agents and informers lived in or visited the building – designed as an experiment in minimalist urban living – between the 1930s and 1950s.
The information has come to light following the release of former East German files, and new information from MI5.
Among the trendy left-wing intellectuals living and partying at the apartment block, known as the Isokon, was a man called Jurgen Kuczynski, an exile from Nazi Germany who was already signed up to the communist cause. He was assisted by his sister Ursula, codenamed Sonya.
In the 1940s she moved to Oxford near the Atomic Energy Research Establishment at Harwell, liaising with a spy called Klaus Fuchs, a German immigrant working at the centre on the manufacture of uranium-235, a vital component of atomic weapons.
In a plot straight out of a James Bond movie, she used a special washing line as an aerial to transmit intelligence to the Soviet regime, giving Moscow a two-year leap forward in its own nuclear programme. Several opportunities to catch Kuczynski and Sonya were missed. Oxford police reported suspicious radio signals to MI5, while warnings about Kuczynksi by a woman called Milicent Bagot in MI5’s counter-intelligence department were also ignored.
Fuchs was caught and put on trial in 1959. Kuczynski and Sonya fled to East Germany the day before his trial.
