[3] In 1942, he was recruited by Egon Bretscher to the British effort to build an atomic bomb (codenamed Tube Alloys) at the Cavendish Laboratory.
[3] By 1944, Tube Alloys had been merged with the American Manhattan Project and French was sent to Los Alamos.
[4][1] When the war ended, French returned to Cambridge University and the Cavendish Laboratory where he joined the faculty at Pembroke College, becoming a fellow and director of studies in natural sciences.
[3][1] French also briefly worked at the newly formed Atomic Energy Research Establishment in Harwell, Oxfordshire.
[3] He left South Carolina in 1962 to take a faculty position in the MIT Physics Department, where he remained until he retired and was named emeritus in 1991.