Between 2005 and 2007, Walker played Atia of the Julii in both seasons of the HBO–BBC2 television series "Rome". Her performance earned her a Golden Globe nomination in 2005 for Best Performance by an Actress in a Television Series – Drama. She next played the sinister Catherine Braithwaite in "Deus Ex Machina", a two-episode story of the BBC television "cold case" crime series "Waking the Dead", which also aired in January 2007. In May 2007, she appeared as Lady Bess Sedgwick in ITV's "Marple": "At Bertram's Hotel", and then played sugar heiress Ellis Samuels in the CBS television drama "Cane", which premiered 25 September 2007.