John McGregor Hill was born on 21 February 1921 in Chester, the son of John Campbell Hill and Margaret Elizabeth Park.

Hill was educated at Richmond County Grammar School, King's College, London and St John's College, Cambridge. In 1947 he married Nora Eileen Hellet with whom he has two sons and one daughter.

Between 1941-1946 Hill served as a flight lieutenant in the RAF to work on radar. Upon leaving the RAF Hill completed his PhD at the Cavendish Laboratory in Cambridge and in 1948 he began lecturing in physics at London University. In 1950 Hill joined the UK Atomic Energy Authority [UKAEA], during his time at UKAEA Hill served on the board as Member for Production, 1964-1967 before being promoted to Chairman, a role he retained from 1967- 1981.

Alongside working at UKAEA, from 1968-1970, Hill served as a member of the Advisory Council on Technology. He also served on the Nuclear Power Advisory Board from 1973-1981, the Energy Commission, 1977-1979 and President British Nuclear Forum, 1984-1992.