An English painter and illustrator. Gammon was born in Petersfield, Hampshire. He declined an offer of a place at the Slade School of Fine Art, but nonetheless had a successful career as a freelance illustrator and writer
 
During World War II he moved his family to South Wales and became a hill farmer. He moved to Somerset in 1958 and became a full-time painter.
 
He originally painted in watercolour, but on holiday in his 60s, he began to use oil paint. His work was influenced by Paul Gauguin and he later worked in the expressionist style. The RWA held a retrospective of his work in 1985, and in 1986 he held the first of five one-man exhibitions at the New Grafton Gallery in London.