In 1948 he became Henry Overton Wills Professor of Physics and Director of the Henry Herbert Wills Physical Laboratory at Bristol. In 1954 he was appointed Cavendish Professor of Physics at Cambridge, a post he held until 1971. He was instrumental in the painful cancellation of the planned particle accelerator because of its very high cost. He also served as Master of Gonville and Caius College, 1959–1966.