He became known for his role Professor Remus John Lupin in Harry Potter and the Prisoner of Azkaban and gave a great performance in the cult film Naked. As a voice actor, he provided the voice of the Earthworm in the 1996 animated film James and the Giant Peach.
In his youth, he wrote and performed his own songs with the rock band, QED, and the punk rock band, Door 66. While playing guitar and attending Highfield High School, he had no desire to become an actor.
He played a supporting role in the Harry Potter films alongside Daniel Radcliffe.