Declassified Security Service files reveal the remarkable undercover life of a female spy who stole America and Britain's atomic secrets and gave them to the Soviets. Born Ursula Kuczynski in Berlin, 'Sonya' was one of the Red Army's most highly trained and sophisticated wireless operators with an illustrious career in espionage already behind her in China, Poland and Switzerland. She arrived in Britain in 1941 after marrying a British man and quickly took up contact with some of the country's most treacherous agents, including the shy genius and atomic scientist Klaus Fuchs and the later-named 'Granny Spy' Melita Norwood. As America and Britain raced to complete a new superweapon, Sonya passed atomic plans and blueprints to the Soviet Union. She led a frantic double life as a German Jewish refugee by day, sending Morse code throughout the night. Sonya died in 2000, and was honoured by Vladimir Putin as a hero of the USSR.