James Nicholas Callis (born 4 June 1971) is an English actor. He is known for playing Dr. Gaius Baltar in the re-imagined Battlestar Galactica miniseries and television series, and Bridget Jones' best friend Tom in the Bridget Jones film series. He appeared in the television series Eureka and 12 Monkeys on Syfy as Dr. Trevor Grant and Athan Cole "The Witness", respectively. Since 2017, he has voiced the character Alucard in the Netflix series Castlevania and Castlevania: Nocturne, based on the video game series of the same name. In 2022, he appeared in season 2 of Star Trek: Picard as Jean-Luc's father in childhood flashbacks.