https://en.m.wikipedia.org/wiki/Ursula_Kuczynski

∼Born Ursula Maria Kucznski in Schoneberg, Prussia,she was destined to become one of the Soviet Union's most successful spies.Also known as Ruth Werner,Ursula Beurton and Ursula Hamburger - her GRU (Intelligence Directorate of the Soviet Army) code name was:Red Sonja, this is the name often used by intelligence services with reference to Beurton.
Beurton was a very effective spy for the Soviet Union and without her exceptional abilities for espionage...The Soviet Union would never have developed the 'A'Bomb so quickly. This is the general opinion of counter espionage organisations in both Britain and the U.S.A.
Beurton joined the communist party at a very early age,she was quietly spoken,very intelligent and a good organiser.She became a spy for the GRU and completed her formal espionage training in Moscow, was active in Manchuria in 1935, then moved to London and later to Switzerland in 1939 - here she operated the Lucy Spy ring.
Beurton moved to Britain in 1941 to continue her activities for the Russian GRU.
Released material from the National Archives, does reveal at this time Beurton was under surveillance by MI5 and her mail was being intercepted. She was a professional spy and obviously would have been aware of this and acted accordingly.
Beurton was the handler for physicist Klaus Fuchs, who passed all his information to Beurton when they met and went for a walk.
After the arrest of Klaus Fuchs in late 1949, Beurton fled Britain for East Berlin. She then retired from espionage for the GRU in 1950- and later received the personal thanks of Joseph Stalin.
Beurton then worked for the East German Government for the next decade and then changed her role and became a writer. Her autobiography:Sonja's Report (made into a film in Russia) and a number of Children's Books.
Awarded: Order of the Red Banner - 1937 and 1969.
Husbands: Rudolf Hamburger and Len Beurton.
Famous Event: Beurton was questioned in 1947 by William Skardon the famous and ruthless MI5 interrogator at her home,The Firs, Great Rollright, Oxfordshire - she gave nothing away and was a 'tough nut' according to MI5 file and her training was very thorough commented Skardon.
It was the opinion of Intelligence Services in both Britain and America that Ursula Beurton was the most effective and committed of all Soviet spies.