James Nicholas Callis (born 4 June 1971) is an English actor. He is best known for playing Dr. Gaius Baltar in the re-imagined Battlestar Galactica miniseries and television series, and Bridget Jones' best friend Tom in Bridget Jones's Diary and Bridget Jones: The Edge of Reason. He later reprised the role in 2016, in Bridget Jones's Baby. He joined the cast of the TV Series Eureka, on Syfy, in 2010. In 2017 he voiced the character Alucard on the Netflix series Castlevania, based on the video game of the same name.