His early films included the cult thriller The Night Digger (1971) and The Darwin Adventure (1972) in which he portrayed the young Charles Darwin. In 1981 he gave his most widely-seen screen performance, as Lancelot in the 1981 film Excalibur. He also appeared in Just Jaeckin's film version of D.H. Lawrence's Lady Chatterley's Lover (1981), playing Mellors, and in Agatha Christie's Evil Under the Sun (1982), the latter reuniting him with Diana Rigg, his co-star in The Misanthrope.