John Copnall was born in Slinford, Sussex, son of the sculptor Bainbridge Copnall.
Studied at the Architectural Association in 1945-46 and 1949-1950 studied with his father at Sir John Cass College. Then at the Royal Academy Schools under Henry Rushbury until 1954. Won the Turner Gold Medal for landscape painting in 1954. Went to live in Spain until 1958. Taught for many years from 1973 at Central School and was a visiting teacher at Canterbury College of Art fro a time. Won an E A Abbey Scholarship in 1970; Arts Council Awards 1972-73; a British Council Award in 1979 and in 1989 elected a London Group member. Showed in many group shows including Royal Academy Summer Exhibitions from 1980. Held a solo exhibition at the Piccadilly Gallery in 1955.Arts Council, Aberdeen and Bristol public galleries and other notable collections hold examples of his work. Lived in London.