John’s university career began at Peterhouse College Cambridge. He graduated in Botany in 1946 and remained at Cambridge to complete his PhD in 1950. From the outset of his career, John was recognised as having an outstanding intellect. In 1948 he went to the California Institute of Technology as an Agricultural Research Council Scholar where he worked with George Beadle, Norman Horowitz and Sterling Emerson in what was a stronghold of Neurospora genetics. Shortly after he married Sterling Emerson’s daughter, Ann, so John’s visit was productive on both a scientific and personal level. He was appointed to a lectureship in the Botany Department of Leicester University in 1950 and was made a Reader four years later. A year as an Associate Professor in the Massachusetts Institute of Technology preceded his appointment as Head of the Genetics Division of the John Innes Institute in 1961. He remained at John Innes until 1966 when he was appointed as Professor and Head of the newly established Department of Genetics at Leeds. In 1976, John was appointed to the Buchanan Chair of Genetics in Edinburgh and was head of the Department of Genetics until 1984 when he moved to take up the Balfour Chair in Cambridge. He is the only person to have held both of these prestigious chairs. On his “retirement” from Cambridge in 1991, John returned to Edinburgh where he continued to take an active part in teaching and research.