She enjoyed a collaboration with Stepney's Half Moon Theatre, appearing in the London première of Dario Fo's We Can't Pay?

In December 2005, she appeared in the London production of the highly acclaimed anti-Iraq War one-woman play Peace Mom by Dario Fo, based on the writings of Cindy Sheehan.

Her many television appearances during the 1980s and 1990s include the 1980 miniseries Flickers opposite Bob Hoskins, the TV version of Duet for One, for which she received a BAFTA nomination, the series A Kind of Living (1988–89), Dennis Potter's Cold Lazarus (1996), and Tom Jones (1997).

De la Tour told Richard Webber, who wrote a 2001 book about the series, that Ruth Jones "was an interesting character to play.

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.

In 2010, she reprised Maxime as a cameo in Harry Potter and the Deathly Hallows Part 1. 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 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.

From 2013 to 2016, de la Tour played the role of Violet Crosby in ITV sitcom Vicious with Ian McKellen and Derek Jacobi.

In 2021, de la Tour appeared in an ITV production, initially released on BritBox - Professor T. - in which she played the mother of the titular character.

[6] An episode of the BBC series Who Do You Think You Are?, first broadcast on 22 October 2015, revealed de la Tour to be a descendant of the aristocratic Delaval family.