He is best known for his roles in films, including Feast of July (1995), The Thin Red Line (1998), Lost Souls (2000), Birthday Girl (2001), Murder by Numbers (2002), Stage Beauty (2004), The New World (2005), Me and Orson Welles (2008), London Boulevard (2010), Twixt (2011), War Book (2014), Snowden (2016), and September 5 (2024).

Taking his stage name from his mother's maiden name,[5] Chaplin began his professional career performing in BBC television dramas in bit parts, and occasional cinema films.

James Ivory and Ismail Merchant cast him as a servant in The Remains of the Day;[6] also in 1992, he appeared in Between the Lines (series 1, episode 1), and as the socially inept Con Wainwright in Feast of July (1995).

[7][8] In the United States, he was cast by director Michael Lehmann as a photographer caught between two women (Uma Thurman and Janeane Garofalo) in the romantic comedy The Truth About Cats & Dogs (1996), a retelling of Cyrano de Bergerac.

After co-starring opposite Michelle Yeoh in the Taiwan-made action film The Touch (2002), Chaplin played George Villiers, 2nd Duke of Buckingham in the romantic drama, Stage Beauty (2004), set in the world of British theatre in the 1660s.

Following a supporting role in the children's fantasy The Water Horse: Legend of the Deep (2007), Chaplin portrayed prominent English stage and film actor George Coulouris in Me and Orson Welles (2009), directed by indie filmmaker Richard Linklater.