Following a BA in mathematics I did my Ph.D. under R A Fisher at Cambridge University and then post- doctoral work under Joshua Lederberg at Stanford. I was on the faculty of the Genetics Department in the Stanford University Medical School from 1962 until 1970 and returned to England in 1970 as Prof of Genetics at Oxford University. In 1979 I became Director of Research, and later Director General, of the Imperial Cancer Research Fund. Since 1996 I have been Head of the Cancer & Immunogenetics Laboratory, Weatherall Institute of Molecular Medicine, Oxford