Dame Maggie Smith, an English actor known for her roles in the Harry Potter films and Downton Abbey, has died aged 89, her publicist said on Friday.

One of the few actors to win the treble awards crown of an Oscar (two), an Emmy (four), and a Tony, Smith's long career started on the stage in the 1950s.

Margaret Natalie Smith was born in Ilford, on the eastern edge of London, on December 28, 1934.

Her father was assigned in 1939 to wartime duty in Oxford, where her theatre studies at the Oxford Playhouse School led to a busy apprenticeship.

She took Maggie as her stage name because another Margaret Smith was active in the theatre.

Her first Academy Award nomination was for her turn playing Desdemona opposite Laurence Olivier's Othello in 1965.

1969's The Prime of Miss Jean Brodie brought her the Academy Award for best actress, as well as the best actress British Academy Film Award (BAFTA). 

Smith added a supporting actress Oscar for California Suite in 1978 — a performance that prompted co-star Michael Caine to say: "Maggie didn't just steal the film, she committed grand larceny."

On stage, she won a Tony in 1990 for Lettice and Lovage.

Smith was knighted in 1990 by Queen Elizabeth II and became a Dame.

For many younger fans in the 21st century, however, she was best known as Professor McGonagall in all eight Harry Potter films, and as Violet Crawley, the Dowager Countess of Grantham, in the hit TV series Downton Abbey — a role that seemed tailor-made for an actress known for purse-lipped asides and malicious cracks.

Her work in 2012 netted three Golden Globe nominations, for the globally successful Downton Abbey TV series and the films The Best Exotic Marigold Hotel and Quartet.

Smith dryly summarised her later roles as "a gallery of grotesques", including Professor McGonagall.

Asked why she took the role, she quipped: "Harry Potter is my pension."

Other critically acclaimed roles included Lady Bracknell in The Importance of Being Earnest, a 92-year-old bitterly fighting senility in Edward Albee's play Three Tall Women, and her part in 2001 black comedy movie Gosford Park.

She received Academy Award nominations as a supporting actress in Travels with My Aunt, Room with a View and Gosford Park, and a BAFTA award for supporting actress in Tea with Mussolini.

She also won Golden Globes for California Suite and Room with a View, and BAFTAs for lead actress in A Private Function, A Room with a View and The Lonely Passion of Judith Hearne.

She married fellow actor Robert Stephens in 1967. They had two sons, Christopher and Toby, and divorced in 1975.

That same year she married the writer Beverley Cross, who died in 1998.

In 2009, she told The Times she had been given the all-clear by doctors after battling breast cancer for two years.

"The last couple of years have been a write-off, though I'm beginning to feel like a person now," she said at the time.

AP/Reuters