Waddell has divided her work between stage and screen. Amongst her roles to date have been her performance as Sasha opposite Ralph Fiennes and Bill Paterson in the Almeida Theatre's London production of Ivanov (1997), Countess Nordston in Anna Karenina (1997), Tess in a London Weekend Television production of Tess of the D'Urbervilles (1998), Julia Bertram in Mansfield Park (1999), Estella in Great Expectations, Nina in a Royal Shakespeare Company production of The Seagull by Anton Chekhov (2000), for which she was nominated for an Ian Charleson award and Molly Gibson in the television mini series Wives and Daughters for which she won a Broadcasting Press Guild Best Actress award. She played Mary Heller in the American film, Dracula 2000. In 2002 she starred in The One and Only. She won a Prism Award for Best Actress for her portrayal of Natalie Wood in The Mystery of Natalie Wood, a 2004 TV movie directed by Peter Bogdanovich. In 2006 Waddell starred alongside Jason Statham and Ryan Phillipe in Chaos. During the same year, she co-starred with Lee Pace in Tarsem Singh’s The Fall.
