Maggie Smith was the grandest of grande dames – and a true cinematic superstar | Peter Bradshaw

Maggie Smith thought she was famous after The Prime of Miss Jean Brodie, in 1969; she gave a glorious, Oscar-winning performance in her mid-30s in the movie based on the Muriel Spark novel, and no actor ever intuited Spark’s world more brilliantly. Smith became the Edinburgh schoolmistress (and, oh dear, the term “schoolteacher” won’t do at all). Her Miss Jean Brodie is imperious, haughty, vulnerable, sexually attractive, prone to admiring fascism and terribly lonely. Her delicate, open face registered a kind of wounded and delusional idealism and poignantly absurd conceit, a complicated, funny portrayal that went above and beyond a hackneyed comedy of “spinsterism”.

Nearly 20 years later, in The Lonely Passion of Judith Hearne from 1987, she played a rather Brodie-esque woman being courted by the unreliable Bob Hoskins; it was a more serious performance, and in 1993, she received a special Bafta for her remarkable screen career.

But it was only in the 21st century, and in the next stage of her life, that Maggie Smith realised that there was a whole new level of screen-celebrity to which she had ascended. For director Robert Altman and screenwriter Julian Fellowes she became the toweringly difficult Countess of Trentham in his prewar country-house drama Gosford Park in 2001, a role that morphed (without much change) into the Dowager Countess of Grantham in Fellowes’s global TV smash Downton Abbey.

Added to that, in the same year, Smith became the kindly teacher Minerva McGonagall in Harry Potter and the Philosopher’s Stone. Professor McGonagall in fact lasered Smith into the minds of children; crotchety, haughty Lady Grantham impressed her (again) on to their parents’ and grandparents’ attention and Smith was now recognised all over the world. She could once go shopping in peace and quiet at her local Waitrose, but then would recount her dismay at being pestered for selfies in New York. Perhaps only the queen herself had a higher icon rating, especially in the United States.

Before she emerged as the grandest grande dame in the world, Smith put her gimlet-eyed wit and theatrical assurance to work in playing vivacious roles in which her sexuality, and the concealment and repression thereof, were of great importance. In the 1978 Neil Simon comedy California Suite, which won her an Oscar for best supporting actress, she was a version of herself: a meta-turn as a British stage star returning from a calamitous awards ceremony and depressed about the decline in her career as she gets older (ironic, considering her own career only got better with age), and her marriage to an in-the-closet gay man, played by Michael Caine.

Fascinatingly, she then played two sexually potent roles in the 1980s opposite Michael Palin. In The Missionary in 1982 she was the sensual Lady Isabel Ames, who effectively controls the purse-strings for Palin’s missionary work in London’s East End and will only open them if Palin submits to her desires; the missionary position being pretty supine, in his case. And in Alan Bennett’s A Private Function two years later, she is the demanding wife of Palin as they plan to defy Britain’s postwar rationing rules by abducting a pig for their own consumption.

It was however in George Cukor’s Travels With My Aunt (1972), adapted from the novel by Graham Greene, that Smith had begun to establish that Wilde-Wodehousian “aunt” persona – at just 38 years old she was easily playing a woman almost twice that. Alec McCowen is the man who is bamboozled by Smith’s Aunt Augusta into a harebrained scheme to rescue her former lover from a kidnap plot. This was the powerful and comically rich Bracknell-esque figure that Smith could modify and evolve in various ways for the rest of her career. In A Room With a View in 1985 she is the disapproving chaperone for Helena Bonham Carter’s Lucy Honeychurch in Italy, a role that got her the Golden Globe for best supporting actress. In Agnieszka Holland’s Washington Square (1997), she is the eccentric Aunt Lavinia. In The Last September (1999) she is Lady Naylor, a matriarch of the Anglo-Irish ascendancy in 1920s Cork, under pressure as Ireland prepares to reject the British. All of these roles gave Smith the chance to establish a performance somewhere on a line between tragedy and absurdity – with a social satire always in the mix. I enjoy these Smith films more than the Werther’s Original-type oldie-sentimental dramas and comedies that she sometimes played, occasionally with a stagey working-class accent, such as The Best Exotic Marigold Hotel in 2011.

Her two late masterpieces, for me, were The Lady in the Van from 2015, in which she played the real-life homeless lady Miss Shepherd, who lived in a van outside Alan Bennett’s house for years. (Shepherd was was very much the heir to Jean Brodie, with her disapproving stare and uncompromisingly high standards.) The other Smith gem is her appearance in the documentary Nothing Like a Dame in 2018, alongside other great theatrical dames Judi Dench, Joan Plowright and Eileen Atkins, in which with absolute honesty and unsentimentality they talk about the acting life. Smith is very funny about the nightmare of working with Laurence Olivier and playing a demure Desdemona to his booming blackface Othello.

Related: Maggie Smith's 20 best films – ranked!

Smith was that unique superstar whose classical stage training and technique fused with an instinctive awareness of the camera lens – flirting with it and disdaining it. Even at her warmest and most approachable she was a performer who was magnificently unaware of modern rules about being relatable; in the smallest of roles she set her own terms and every other actor was her satellite. She had been a legend since the late 60s, no one deserved the description more.