Of all her TV roles, however, she is best known for playing spinster Ruth Jones in the successful Yorkshire television comedy "Rising Damp", from 1974 to 1978. De la Tour told Richard Webber, who penned a 2001 book about the series, that Ruth Jones "was an interesting character to play. We laughed a lot on set, but comedy is a serious business, and Leonard took it particularly seriously, and rightly so. Comedy, which is so much down to timing, is exhausting work. But it was a happy time." Upon reprising her "Rising Damp" role in the 1980 film version, she won Best Actress at the Evening Standard Film Awards. In the mid-1980s, de la Tour was considered, along with Joanna Lumley and Dawn French, as a replacement for Colin Baker on "Doctor Who". The idea was scrapped and the job was given to Sylvester McCoy. In 2003, de la Tour played a terminally ill gay woman in the film "Love Actually" with the actress Anne Reid, although her scenes were cut from the film's theatrical release and appear only on the DVD. In 2005, she portrayed Olympe Maxime, headmistress of Beauxbatons Academy, in "Harry Potter and the Goblet of Fire". Notable television roles during this time include "Agatha Christie's Poirot: Death on the Nile" (2004), "Waking the Dead" (2004), the black comedy "Sensitive Skin" (2005), with Joanna Lumley and Denis Lawson, "Agatha Christie's Marple: The Moving Finger" (2006) and "New Tricks" as a rather morbid Egyptologist, also in 2006. She was nominated for the 2006 BAFTA Award for Actress in a Supporting Role for her work on the film version of "The History Boys". She later appeared in several well-received films, including Tim Burton's 2010 "Alice in Wonderland" as Aunt Imogene, a delusional aunt of Alice's, opposite Johnny Depp, Anne Hathaway, Helena Bonham Carter, and Mia Wasikowska and a supporting role in the film "The Book of Eli", directed by the Hughes brothers. In 2012, she appeared in the film "Hugo". Until 2012, she was also a patron for the performing arts group Theatretrain. From 2013 to 2016, de la Tour played the role of Violet Crosby in ITV sitcom "Vicious" with Ian McKellen and Derek Jacobi. From 2013 to 2014, she portrayed headmistress Ms Baron in the BBC One sitcom "Big School".