A day I have been dreading is now upon us: Dame Maggie Smith has died.

She was 89, of course, and spent much of her final acting years playing women who were facing the inevitable: Her iconic Violet Crawley, Dowager Countess of “Downton Abbey,” confesses she is ill in the first follow-up film and dies in the second. The reformed racist Muriel Donnelly of “The Best Exotic Marigold Hotel” bids a fond farewell to those she has aided in “The Second Best Exotic Marigold Hotel.” In “The Lady in the Van,” the tragedy of Smith’s odorous squatter Mary Shepherd is revealed only after her surprisingly touching death. And while the disabled Lily Fox survives “The Miracle Club,” which would be Smith’s final film, she does so with a late-in-life reconciliation prompted by a visit to Lourdes.

So she offered us all a long goodbye, did Maggie Smith. Her career spanned seven decades; two centuries; stage, screen and television and virtually every genre, from Shakespeare to “Harry Potter” and her brilliance never dimmed. No matter the general state of the project she was in, Smith never failed to illuminate, astonish and entertain.

After watching “The Miracle Club,” I looked up her age — my profession cultivates the grim habit of keeping track of prewritten obituaries — and I could practically hear her saying in that wry, truth-telling grumble: “Not long now.”

Still, it is a seismic event, a bitter shock: If anyone was going to live forever, it would have been Maggie Smith.

Who else would have the temerity to admit unapologetically that though she “owned the box set,” she had never watched “Downton Abbey”? Who else would, in the documentary “Tea With the Dames” accuse British national treasure (and good friend) Judi Dench of stealing all the good parts for women of their age. (“Don’t turn on me,” Dench says, laughing. “I’m turning on you,” Smith replies with a sidelong glance. “It’s all coming out now.”) Who else could bring the same air of affronted temerity to a homeless woman living in an unspeakably filthy van as she had to a parade of aristocrats and socialites, divas and fluttering single ladies.

It was far too easy to imagine Smith confronting the specter of death with a raised eyebrow and, after pausing for a moment of outraged silence, announcing that the timing was far too inconvenient.

The loss of our idols, no matter their age, is always a form of heartbreak — the world was certainly a richer, livelier place with Maggie Smith in it and now she is not. In many ways, she helped redefine what it meant to grow old, particularly for women. The face and body may change, but the spirit need not falter, the desire and ability to do what you love need never abate.

I didn’t have the opportunity to see her onstage, but on screens large and small she was unshakable as she was elastic: the radiant if misguided passions of “The Prime of Miss Jean Brodie,” the desperate wit of the heart-sore star in “California Suite,” the dithering, half-hearted tyranny of the companion in “A Room With a View,” the sponging snobbery of the impoverished relation in “Gosford Park” — honestly, one could go on and on (and on). In her later life, she often complained about her frequent appearance in period pieces, but her roles defy any type of category beyond the fact that once she played them, they belonged to her completely, the genre of Maggie Smith.

It has become absurdly common for people who should know better to say that it was the “Harry Potter” franchise and “Downton Abbey” that brought Smith, already a winner of two Oscars, a Tony an Emmy and seven BAFTAs, international fame when, at least in the case of “Downton,” it was the other way around.

It is difficult to imagine that “Downton,” even with its exquisite period-piece world-building, solid cast and deft writing, would have achieved astonishing-hit status without Smith at its center. As the tart-tongued Dowager Countess of Grantham, she was “Downton’s” superpower — able to freeze a room with a glance, break your heart with the twitch of a shoulder and sum up the the entire theme of the series in just four words — ”What is a week-end?” She was funny, she was formidable and she held the audience, as she held the family, in the palm of her hand. Other main characters could come and go, but without a regular dose of Smith’s Violet, there would be no “Downton.”

Smith, who often claimed she had never watched the show and found the rigors of filming, not to mention the weight of all those hats, exhausting, had, toward the end of her career, gained a reputation for being, if not difficult than certainly intimidating, on set.

In “Tea With the Dames,” some of that is apparent, as she waves away an on-set photographer or complains about uncomfortable seats or describes her often contentious relationship with Laurence Olivier during her days at the National Theater. During one production, Olivier told her she was delivering her lines so slowly that it “bored him off the stage.” So during the next show, she said, she spoke so quickly that “he didn’t know if it was Wednesday or Christmas. … I got him really rattled.” He terrified her, she said, but “I think I scared the wits out of him from time to time.”

But there’s also a moment when she and Dench are asked if first days on set are still scary. “All days are scary,” Smith says immediately. “I don’t know why people assume that it is any other way. Filming is very scary because there are so many people involved. Everybody waiting with bated breath and if you get it wrong, there’s a lot of silent looking at each other and the eyes roll and there,” she sighs dramatically, “‘are we really going again?’”

It is quite difficult to imagine anyone rolling their eyes or sighing if Maggie Smith got something wrong, almost as difficult as imagining such an event actually occurring. That’s how good an actor she was. Whatever she did, she hit the perfect note with such confidence that to even think it might be the result of several takes seems outrageous.

So one can only assume that if death came for Maggie Smith, it was only because she allowed it.

“Dead?” her homeless Mary Shepherd protests to Alex Jennings’ concerned Alan Bennett in “The Lady in the Van.” “You’ll know when I’m dead.”

Now as nations mourn and tributes pile up, as her work is praised, characterized and categorized, as we come to grips with the fact that we will never have a chance to see what she would have done next, we very much do.