In 1996, Mortimer appeared in her first feature film opposite Val Kilmer in "The Ghost and the Darkness", and in the coming-of-age story, "The Last of the High Kings." In 1998 she appeared as Kat Ashley in "Elizabeth", and played Miss Flynn in the television mini series "Cider with Rosie", which was adapted for television by her father. In 1999, she played three roles: she was the "Perfect Girl" dropped by Hugh Grant in "Notting Hill"; Esther in the television miniseries "Noah's Ark," and the actress Angelina in "Scream 3".