As Desdemona in Othello, Professor McGonagall in Harry Potter or the Dowager Countess in Downton Abbey, her acerbic wit, perfect timing and the twinkle in her eye endeared her to millions.
Dame Maggie Smith, who has died just three months away from her 90th birthday, could turn on a dime.
In doing so, she could make an audience ache with laughter one moment and well up the next.
Her friend and longtime collaborator, writer Alan Bennett, told the New York Times Magazine in 1990: The boundary between laughter and tears is where Maggie is poised always.
She had a more varied career and style than any other actress of her generation. She was unpredictable, prim and proper, with laughter bubbling under the surface and perfect comedic timing.
More than that she was fierce - allegedly so fierce that director Chris Columbus sent Daniel Radcliffe to collect her from her trailer while filming Harry Potter because he was afraid of her.
Dame Maggie Smith as Professor Minerva McGonagall in fourth Harry Potter film the Goblet of Fire
Dame Maggie in the title role in 1969 film The Prime of Miss Jean Brodie
Dame Maggie Smith in 1995 with her second husband Beverley Cross, who died in 1998
She was a joy to watch in whatever role she took on - unless she was bored.
She starts divinely and then goes off rather like cheese, said Jeremy Brett, who acted with her at the National Theatre. She finds it very difficult to sustain parts.
Her skill was so formidable she sometimes became annoyed with those she felt couldnt play their parts well.
Playwright Ronald Harwood said: If Maggie likes another actors kind of acting, shell do anything to help that performance; if she finds it in any way boring or tedious, that other actor might as well not exist.
Dame Maggie once told the New York Times Magazine: Its true I dont tolerate fools but then they dont tolerate me, so I am spiky. Maybe thats why Im quite good at playing spiky elderly ladies.
But criticism of Dame Maggie is rare. Simon Callow, who worked alongside her in the 1985 film A Room with a View, told the BBC: Its to do with her absolutely extraordinary mind… I dont think there is another actor on earth who can make you see what she is talking about.
The only person who did not like to watch Dame Maggie act was herself.
She even told the BFI: I have never watched Downton, it got to a point where it would have taken too long to catch up.
Dame Maggie Smith portraying Desdemona in the production of Shakespeares Othello
Dame Maggie with her first husband Robert Stephens and their young son Christopher in 1970
Jill Bennett, Tom Jones and Maggie Smith (left to right) with their silver hearts showbusiness awards from the Variety Club of Great Britain at the Savoy Hotel in London on March 11, 1969
Queen Elizabeth II being presented to Dame Maggie Smith by Sir Laurence Olivier, when the Queen attended the charity premiere of the film Othello at the Odeon Theatre in London, on May 2, 1966
Dame Maggie Smith rehearsing for Peter Pan with Dave Allen in an undated photograph
Dame Maggie Smith and Dame Judi Dench arriving at the Theatre Royal Haymarket in London on December 9, 2001
Dame Maggie was born in Ilford in 1934 and moved to Oxford when she was five.
Her parents - a pathologist and a secretary - did not encourage her acting and, much to her annoyance, she was never in any school plays.
She told the Evening Standard: Honest to God, I have no idea where the urge [to act] came from.
It was such a ghastly time and we didnt go to the theatre. I got into terrible trouble once because the neighbours took me to the cinema on a Sunday.
Instead it was one of her teachers at the all-girls Oxford High School, Dorothy Bartholomew, who also taught Miriam Margolyes - who encouraged her.
At 17 she enrolled on an acting course at the Oxford Playhouse and made her debut with the Oxford University Dramatic Society as Viola in Twelfth Night.
Her future husband Beverley Cross met her after the performance and proposed, but she turned him down as he was still married.
They stayed close friends and finally married 23 years later.
After Oxford, Dame Maggie went to America with the revue New Faces Of 56.
Remembering the time in an interview with CBS she said: The thing that astonished me more than anything was the food - we hadnt long stopped rationing in England, so when I ordered anything to eat I was a nervous wreck because it would be mountainous.
Back in the UK in 1963 she was recruited to join Laurence Oliviers National Theatre Company at The Old Vic.
She starred opposite Olivier as Desdemona in Othello and Hilde Wangel in Ibsens The Master Builder.
Dame Maggie counted Olivier and his wife Joan Plowright as friends but found the acting great to be a very competitive performer.
She married her first husband in 1967, fellow actor Sir Robert Stephens, and had two sons, Chris in 1967 and Toby in 1969, who chose the same career as their parents.
Stephens and Dame Maggie was an alcoholic and had numerous affairs.
His behaviour prompted her to divorce him in 1975 and marry Beverley Cross the following year.
The break-up marked the end of what was then one of theatres most illustrious husband-and-wife acting teams.
Their on-screen partnership was best known through the film The Prime of Miss Jean Brodie, in which they starred opposite each other.
Dame Maggie Smith played the Dowager Countess of Grantham in Downton Abbey
Maggie Smith alongside Miriam Margolyes, Richard Harris and Alan Rickman in 2002 film Harry Potter and the Chamber of Secrets
Dame Maggie Smith in the 1976 film Murder By Death which also starred Alec Guinness
Dame Maggie Smith in the royal box at the Wimbledon Championships on July 11, 2019
Dame Maggie won a Best Actress Oscar for her role in the film.
After Dame Maggie filed papers, Stephens said: She really should have married him in the first place. She was engaged to him for three years when I met her.
Of course I have regrets about our marriage. One always has it its failed.
But it was me. It was my fault. I blame myself for too little responsibility.
Her reunion with Cross came 23 after he first proposed to her in Oxford. Dame Maggie was Cross third wife.
They moved to Canada, where she played Cleopatra and Lady Macbeth at the Stratford Shakespeare Festival in Ontario.
She won her second Oscar - Best Supporting Actress - in California Suite in 1979.
Dame Maggie also won five Baftas (including a record four for Best Actress), four Emmys, and a Tony Award.
She was made a Dame by Queen Elizabeth in 1990.
As well as two Oscars, by the end of her life she had won five Baftas (including a record four for Best Actress), four Emmys, a Tony Award and was made a Companion of Honour by Queen Elizabeth II.
She played Professor Minerva McGonagall in Harry Potter from 2000 to 2010 and then the Dowager Countess in Downton Abbey from 2010 to 2015.
She told CBS: I am deeply grateful for the work in Potter and indeed Downton but it wasnt what youd call satisfying. I didnt really feel I was acting in those things.
The most tormented thing I ever did was sit in the snow for about a week with that daft hat on my head for Harry Potter. Sitting in that trailer day after day and not being used doesnt make you feel too jolly.
Dame Maggie was diagnosed with breast cancer in 2007, while filming Harry Potter and The Half-Blood Prince, the sixth instalment in the eight-part franchise.
She was given the all-clear after undergoing two years of treatment, including chemotherapy.
Downton Abbey in 2010 was the first time she was truly famous, she said: Ive been working around for a very long time before Downton and life was fine, no one knew who the hell I was, and it has now changed.
She long lamented the lack of roles for older women, a fact she in part attributed to her friend Dame Judi Dench.
She told the BFI: Judis always there, what can you do? It was Joan Plowright who said that to me: "There are parts, but Judes always got her paws on them first."
Sir Robert died in 1995 and Cross in 1998, Dame Maggie did not remarry.
Speaking about Cross, she told the Guardian in 2004: I still miss him so much its ridiculous. People say it gets better but it doesnt. It just gets different, thats all.
Dame Maggie once summed up her life with the phrase: One wanted to act, one started to act, and ones still acting.
But her life was so much more than that, she brought laughter and tears into the cinemas, theatres and homes of the world and was a true British icon.