His career in films began in 1933 working as an assistant
art director with
Michael Balcon, who was working as an art director for
MGM-British and Warner Brothers. In 1942 Relph joined Ealing as chief
art director, working mainly on
Basil Dearden's films. He was a producer
and occasional writer. After producing
Kind Hearts and Coronets (1949), he began his long, prolific partnership with Dearden, up until
Dearden's death in 1971. Sometimes credited as a joint director with
Dearden,
Davy (1957) is regarded as his directorial debut.