Born in London he is the son of Tom and Winifred Gentlemen, two artists who met at the Glasgow School of Art. Following national service – in the Royal Army Education Corps teaching art in Cornwall he studied at the Royal College of Art under Edward Bawden and John Nash. After two further years teaching there he vowed never again to teach or collaborate with other artists.
His early works included wood engravings for Penguin paperbacks. Amongst his later achievements are 103 stamps for the Post Office between 1962 (for National Productivity Year) and 2000 (for the Millennium); posters for – inter alia – London Transport, the National Trust and the Imperial War Museum; the 1978 Eleanor Cross murals at Charing Cross underground station; several works for the Oxford Almanac; and six ever-popular lavishly illustrated travel books.