Known for his roles as Tony Blair in The Queen and David Frost in Frost/Nixon. He also appeared in the 1992 stage adaptation of Romeo and Juliet and played a role in the 2010 film, The Special Relationship. In 2013, he began playing Dr. William Masters on the Showtime series Masters of Sex.
He spent a year employed at a Welsh fast-food restaurant called Burger Master to support his acting career.
His parents, Irene Thomas and Meyrick Sheen, both worked as actors. He had a daughter named Lily with actress Kate Beckinsale, whom he was in a long term relationship with. He also dated actresses Rachel McAdams and Sarah Silverman.
He co-stars with Lizzy Caplan on the Showtime drama series Masters of Sex.