He was born Reginald Truscott-Jones in Neath, Wales, and took his stage surname from an area of the town.
The pinnacle of his career came in 1946 when he won an Academy Award for Best Actor for his portrayal of an alcoholic in the film The Lost Weekend. Playing opposite Grace Kelly in Hitchcock's Dial M for Murder (1954), his popularity later slumped and he was reduced to playing in low-budget horror movies such as The Man with X-Ray Eyes.