Richardson had originally intended to study veterinary medicine, but her squeamishness made this impossible. She enrolled at the world famous Bristol Old Vic Theatre School, where she studied alongside Daniel Day-Lewis. In 1981, she made her stage debut in Moving at the Queen's Theatre in London.
Three years later, she made her big screen debut as platinum blonde nightclub hostess Ruth Ellis, the last woman to be hanged in the United Kingdom in Mike Newell's critically acclaimed biographical drama, Dance with a Stranger. Her performance in that film won her much praise, and within a year, she had been cast by Steven Spielberg to appear in his World War II drama Empire of the Sun (1987).
Richardson is perhaps best known for her role as infantile Queen Elizabeth I, aka Queenie, in the cult British comedy Blackadder. Other television roles include the bitchy Pamela Flitton in A Dance to the Music of Time (1997), Miss Gilchrist in St. Ives (1998), Bettina (the obsessive compulsive interior decorator) in Absolutely Fabulous, The Wicked Stepmother Hallmark's Snow White: The Fairest of Them All, along with Kristin Kreuk (2001) and the emotionally repressed Queen Mary in The Lost Prince (2003).
As well as a number of high profile supporting roles in the cinema, including Vanessa Bell in The Hours, Lady Van Tassel in Sleepy Hollow and Patsy Carpenter in The Evening Star, she has also won acclaim for her performances in The Crying Game and Enchanted April, for which she won a Golden Globe, beating a quartet of Hollywood heavyweights: Geena Davis, Whoopi Goldberg, Shirley MacLaine and Meryl Streep.
Two Academy Award nominations (for Damage and Tom & Viv) have not altered the actress's modesty. She refuses to discuss her private life in interviews, and takes both leading and supporting roles in a variety of different genres.
Her extensive film credits have included worthy stints in a number of critically acclaimed independent features, among them Robert Altman's Kansas City (1996), Robert Duvall's The Apostle (1997) and Richard E. Grant's Wah-Wah (2005). In 2002, she wowed critics with a triple-role stint (as Mrs Cleg, Yvonne and Mrs Wilkinson in a hallucination) alongside Ralph Fiennes in David Cronenberg's acclaimed thriller Spider, a film that won Richardson a bevy of international critics awards.
More recently, Richardson appeared as Queen Rosalind of Denmark in the Julia Stiles vehicle The Prince and Me, and the ballet mistress Madame Giry in the long-awaited film version of The Phantom of the Opera, starring Gerard Butler and Emmy Rossum. Her most recent screen incarnation include Rita Skeeter, the toxic Daily Prophet journalist in Harry Potter and the Goblet of Fire, Nana Mae Frost in the the ensemble piece Southland Tales, and as Catherine Kenney in Spinning the Bottle, starring Sarah Jessica Parker and Beau Bridges.