Physicist, born on 27 May 1897 at Todmorden, Yorks and educated at Todmorden secondar school. After war service he graduated at Manchester University in 1920 with a first class in electrical engineering, was awarded a scholarship at St. John's College, Cambridge, where he graduated in mathematics and became a research student under Ernest Rutherford at the Cavendish Laborarory. With E.T.S. Walton in 1932 he developed a high-voltage generator for use as a particle accelerator, which was used to split lithium and other atoms and for which they were jointly awarded the Nobel Prize for physics in 1951. In 1939 he was appointed to a professorship in natural philosophy and elected FRS. During the war years he was involved in the development of radar and other scientific war projects, and his work on nuclear physics contributed to the development of the atomic bomb. From 1946 to 1958 he was Director of the Atomic Energy Research Establishment at Harwell. He was British representative at two United Nations conferences in Geneva in 1955 and 1958 on the peaceful use of atomic energy. He then became the first master of the new Churchill College, Cambridge. He was President of the Manchester College of Science and Technology 1961-1967 and Chancellor of the Australian National University at Canberra 1961-1965. He gained many honorary degrees, was made CBE in 1944 and KCB in 1953, and awarded the Order of Merit in 1957. He was President of the British Association in 1962.
His obituary in The Times described him not only as 'one of the world's leading scientists', but 'one of the most reliable and upright human beings of his time'. Both he and his wife, (Eunice) Elizabeth (née Crabtree) were lifelong members of Todmorden Central Methodist Church, where he was given the freedom of the town in 1947. His interests included architecture and music. He died in Cambridge on 18 September 1967 and a memorial service was held in Westminster Abbey on 17 October.