The British Ethel RosenbergInteresting
story here, but I gotta wonder why she was never prosecuted.
It is known that many of the technical documents she passed to the Soviets found application in Soviet technology, and in the post-World War II era, her information contributed to the Soviet nuclear arms program. She came to be regarded by her handlers in the KGB as their prize spy, possibly more highly regarded than fellow traitor - and defector - Kim Philby. Honors (the Order of the Red Banner) and thanks - and a pension of £20 a month - were all she ever accepted for her services.