Mafham played Mortimer Lightwood in the BBC's 1998 adaptation of Charles Dickens' Our Mutual Friend. Much of the story is seen from Mortimer's perspective. Our Mutual Friend was acclaimed worldwide, and won four BAFTAs including Best Serial. It was nominated for four more BAFTAs, as well as awards from the Royal Television Society, the Broadcasting Press Guild and the San Francisco International Film Festival. In 1999 he played Grahame Tranter in the Midsomer Murders episode "Death of a Stranger."