John Trevelyan est né le 11 juillet 1903. Il était marié à Rosalie Evelyn Lopez-Salzedo, Jean Mutch, Joan Frieda Scott et Kathleen Margaret Pass. Il est mort le 15 août 1986 à Londres, Angleterre, Royaume-Uni.
British film executive, a parson's son. A former teacher and educational administrator, he became secretary of the British Board of Film Sensors (1958-71). In that capacity, he was responsible for a more liberal attitude towards controversial subjects.