Russia was not involved in the Manhattan Project, which saw the atom bomb developed as a weapon of war. Nevertheless, after the Japanese surrender in 1945, it took the Soviets a mere two years to gain entry to this exclusive nuclear club – thanks, in large measure, to a female spy codenamed ’Sonya’.

Already an experienced espionage operative, Berlin-born Ursula Kuczynski arrived in Britain in 1941 as a German Jewish refugee, made contact with other Communist sympathisers and began transmitting information to Moscow by Morse code. Eventually escaping to East Berlin, Kuczynski lived on for another half-century. Absorbing docudrama THE SPY WHO STOLE THE ATOM BOMB (Tuesday 31st, 7.30pm) examines how a seemingly ordinary housewife and mother succeeded in passing on secrets for several years, despite being known to MI5.