Gavin was born and educated in Birmingham. For two years he served as a RAF pilot before going up to Cambridge, where he edited Varsity, the university newspaper. After working for Picture Post, the Sunday Graphic and the BBC, he began his first novel, The Wrong Side of the Sky, published in 1961. After four years as Air Correspondent to the Sunday Times, he resigned to write books full time. He was married to the well-known journalist Katherine Whitehorn and they lived in London with their children.