Sir Joseph Rotblat KCMG CBE FRS was a Polish physicist, a self-described "Pole with a British passport". Rotblat worked on Tube Alloys and the Manhattan Project during World War II, but left the Los Alamos Laboratory after the war with Germany ended. His work on nuclear fallout was a major contribution toward the ratification of the 1963 Partial Nuclear Test Ban Treaty. A signatory of the 1955 Russell–Einstein Manifesto, he was secretary-general of the Pugwash Conferences on Science and World Affairs from their founding until 1973, and shared, with the Pugwash Conferences, the 1995 Nobel Peace Prize "for efforts to diminish the part played by nuclear arms in international affairs and, in the longer run, to eliminate such arms."

https://en.wikipedia.org/wiki/Joseph_Rotblat