The Pontecorvo Affair: A Cold War Defection and Nuclear Physics

In the fall of 1950, newspapers around the world reported that the Italian-born nuclear physicist Bruno Pontecorvo and his family had mysteriously disappeared while returning to Britain from a holiday trip. Because Pontecorvo was known to be an expert working for the UK Atomic Energy Research Establishment, this raised immediate concern for the safety of atomic secrets, especially when it became known in the following months that he had defected to the Soviet Union. Was Pontecorvo a spy? Did he know and pass sensitive information about the bomb to Soviet experts? At the time, nuclear scientist , security personnel, Western government officials, and journalists assessed the case, but their efforts were inconclusive and speculations quickly turned to silence. In the years since, some have downplayed Pontecorvo’s knowledge of atomic weaponry, while others have claimed him as part of a spy ring that infiltrated the Manhattan Project.