Big-screen roles include Four Weddings and a Funeral, Eat Pray Love, Emma, Dancing at Lughnasa, Gosford Park, Fat Slags, Relative Values and Morris: A Life with Bells On. Thompson appeared in Harry Potter and the Deathly Hallows in 2010, as Mafalda Hopkirk and Hermione Granger disguised as Hopkirk. Thompson starred alongside popular British comedians Alan Davies, in Jonathan Creek, and Lee Evans in So What Now? She has also appeared in Persuasion, Midsomer Murders, The Adventures of Sherlock Holmes, A Harlot's Progress, and the TV movie Magnolia. She played Miss Bartlett in Andrew Davies' 2007 adaptation of E.M. Forster's A Room with a View and also appeared in the last episode of series 4 of Doc Martin.