He was educated at Worthing High School for Boys and was, during his schooldays, a member of an amateur dramatic society.
In 1943, he was awarded a State Scholarship and went to St John's College, Cambridge, where he read Mathematics/Natural Sciences.
Gill worked at the National Physical Laboratory from 1947 to 1950, where he met his wife, Audrey Lee, whom he married in 1949.
[1] He gained a PhD in 1953 and, following a year as Visiting Assistant Professor at the University of Illinois, Urbana, joined the Computer Department at Ferranti Ltd.
[2][3] This was later merged into the Imperial College Centre for Computing and Automation, which Gill became director of, whilst he worked as a consultant to the Ministry of Technology.