He was the author of the stage farce Running Riot and played Patricia Routledge's character's husband in Hetty Wainthropp Investigates (1996–1998).
Arguably, Benfield's best known character portrayal was as transport company foreman Bill Riley in the UK television series The Brothers in the early 1970s.
Some of his other television roles included Walter Greenhalgh in Coronation Street (1961–1969), Albert the Clerk in Rumpole of the Bailey (1978–80), and characters in Breakaway (1980) and First of the Summer Wine (1988).
His plays included the farces Post Horn Gallop and Wild Goose Chase, both about the fictional exploits of the eccentric Lord and Lady Elrood and visitors to their castle.
He also appeared with Colin Baker as John Hallam in the Doctor Who audio play Catch-1782 produced by Big Finish Productions.