After graduating, Sewell was set up with an agent by Judi Dench, who had directed him in a play while at the Central School of Speech and Drama. His breakthrough year was in 1993, in which he starred as the nasty Tim in Michael Winner's film Dirty Weekend. Winner chose him after seeing him in a play at the Criterion Theatre. Also in 1993 Sewell starred in the BBC serial of George Eliot's Middlemarch and on stage in Tom Stoppard's play Arcadia at The Royal National Theatre (Lyttelton). His film work includes 1995's Cold Comfort Farm, directed by John Schlesinger, the lead role of John Murdoch in the science fiction film Dark City in 1998, Amazing Grace, The Illusionist and Nancy Meyers' romantic comedy The Holiday. Amazing Grace deals with william Wilberforce's political fight to abolish slavery in Britain, with Sewell playing Wilberforce's co-campaigner Thomas Clarkson. Sewell is known for his villainous roles, such as those in A Knight's Tale, The Legend of Zorro, Bless the Child, Helen of Troy and The Illusionist. He spoke of his unhappiness about this, saying that "[I] don't want to play a baddie again." "Everyone has their thing they have to get around", notes Sewell. "With me, it's like okay, how can I make this upper class bad guy in the 19th century different and interesting?"