In 1989 Whitlock played his most notable role, that of Sydney Chaplin, the elder half-brother of Charlie Chaplin, in the television movie Young Charlie Chaplin by Bazz Taylor. Further well-known series where he had roles were Split Ends, EastEnders, Harry Enfield's Television Programme, Lovejoy, Soldier Soldier, Boon, Grange Hill, A Touch of Frost, The Detectives, Silent Witness, McCallum, Casualty, London's Burning, and The Bill. In 2007 he played a policeman in Sweeney Todd: The Demon Barber of Fleet Street which starred Johnny Depp and Helena Bonham Carter. In 1992, Whitlock also starred in the W.I.Z. directed short film for Flowered Up's song "Weekender", playing the role of Little Joe.