NEW YORK, NY.- “Oh, for heaven’s sake!” Maggie Smith said in a 2015 interview, waving her hands vigorously in front of her face at the suggestion that she was a “national treasure.”

But Smith, who died Friday at 89, was that very thing, an actor who embodied a quintessentially British character: the imperious, commanding woman, be it an aristocrat or a schoolteacher, who smites the less certain or socially secure with her arrow-sharp wit and finely honed disdain, though delivered in suitably plummy tones.

While she worked steadily in theater from the start of her acting career in the 1950s, Smith didn’t become famous until she won an Oscar for her performance in the 1969 film “The Prime of Miss Jean Brodie.” Early on, she later recalled, she had signed a contract with a film company and received a message from the studio publicity department: “Your fan mail total for this month is nil.”

Even after her breakout performance, her fame was mostly among theater and film cognoscenti, who adored her expressive physicality, brilliant comic timing and subtly moving revelations of character. In 1990, Smith was made a dame of the British Empire. But it wasn’t until Smith was in her 60s, cast as Minerva McGonagall in the “Harry Potter” movies, then in 2010 as Violet Crawley, dowager countess of Grantham, in the “Downton Abbey” television series, that she achieved global fame.

“What is a … weekend?” the countess asked in a tone that exquisitely mixed contempt with a soupçon of interest, in one of the first episodes of the show. The line (all credit to the show’s creator, Julian Fellowes) and her delivery summed up her appeal to the enormous “Downton” audience, who couldn’t get enough of Smith’s witty, acerbic character.

“It’s been ludicrous, and I’m having a stop,” Smith said of the celebrity status that her role in “Downton” had brought about. That was during the 2015 interview, and I was talking to her about “The Lady in the Van,” a film written by Alan Bennett, her great friend whom she insisted on having with her. (It should be noted that my teenage children, indifferent to most of my interviewees, were beside themselves when I said I was going to interview Smith.)

Her character in “The Lady in the Van” was the opposite of the countess of Grantham: the unwashed, obstreperous Mary Shepherd, who parked her van in Bennett’s driveway and stayed there for 15 years. In person, Smith wasn’t much like either extreme, but rather friendly, also seemingly bemused and slightly irritated by her new fame. “It’s too much really,” she said. “I want to go to the supermarket in peace, and then you feel bad if you ignore people when they come up to you.”

She was clearly at ease with Bennett, a quiet, self-deprecating and very funny presence. Together they lobbed memories at each other of his 1985 film, “A Private Function,” in which Smith’s character, fed up with a life of poverty in postwar Britain, urges her husband (Michael Palin) to steal a pig, and of their time working on the stage version of “The Lady in the Van” in 1999. There were anecdotes about the three pigs on the “Private Function” set — “none had any talent at all,” Smith said straight-faced — and a quick discussion of her character’s voice when I asked Bennett if he had immediately thought of Smith for that film.

“I don’t think there was anyone else in the frame,” Bennett said.

“What did you think she sounded like?” Smith asked, interested.

“Middle class, slightly squeaky,” he said.

“A dead ringer for me, then,” Smith said. They shrieked with laughter.

This article originally appeared in The New York Times.