Public interest in the late Lady Diana Spencer has never seemed to wane since it was first announced she was to marry Prince Charles. After her turmoil-laden marriage and tragic and untimely death, people still can’t get enough about the People’s Princess and her story.

With director Pablo Larrain’s second foray into a stirring portrait study of a woman behind the throne (his first being 2016’s “Jackie” highlighting Jackie Kennedy), he takes on Diana’s story, focusing on just three days of it — Christmas at Sandringham right before she and Charles divorce.

Larrain deftly handles a hyper-focused and sometimes incredibly vague script by Steven Knight, and couples it with a striking performance by Kristen Stewart and brilliant production value allowing the film to click mostly into place.

Stewart stars as Diana Spencer herself, adopting all of her mannerisms and speech patterns with ease while keeping the run of emotions the Princess of Wales is going through just behind her expressive eyes. And boy, are there a lot of emotions.

Set over the three days from Christmas Eve to Boxing Day 1991, “Spencer” starts with a military convoy delivering a mountain of food hampers to the estate before any of the royal guests arrive for the holiday. In the stout but wide kitchen, we see a sign reminding all staff to keep noises to a minimum, “they” can hear them. Indeed, as the film progresses, the point is made again and again that all conversations are heard, and no secrets can be kept that way.

While the guests arrive with their protective services and lines of cars surrounding them, Diana drives alone in her Porsche, lost on her way to the festivities. With the cold December wind in her hair, she looks completely free on the winding country roads that she drives down looking for Sandringham. Eventually she runs into the estate’s head chef, the sympathetic Darren (Sean Harris) who informs her she’s late. But before he can guide her back, she spots a scarecrow in a field wearing her father’s old coat and decides to take the ratty garment for herself.

When she finally arrives at Sandringham, she’s met with a new member of the Queen’s staff, Major Alistar Gregory (Timothy Spall) who gently forces Diana to take part in a traditional weighing-in, where every member of the royal family’s weight is recorded before the holiday and after to see how many pounds they’ve packed on. “A lovely bit of fun” Gregory jokes, but when you have an eating disorder like Diana, it’s much less so.

After that triggering event, Diana purges in the bathroom before meeting with the family, along the way getting stopped by her royal dresser Maggie, (Sally Hawkins), a friend and confidant to the royal. Maggie has every dress that has been selected for each and every event of the holiday for Diana.

Diana fight’s back tears as she leaves Maggie, gathering with the rest of the family for sandwiches (their entire schedule seems to revolve around meals and eating). With Diana already at her breaking point upon arrival, she quickly spirals, believing she’s seeing Anne Boleyn wandering the halls, imagining situations and the noose of this life around her neck tightening with every rule and regulation thrown her way in this ornate palatial prison.

This whole world is chipping away at Diana, with everyone but herself involved in every decision about her life, from her clothes to driving her car. And with so much of her self-worth diminished, she sees the writing on the wall — to continue this way of life means the end of hers. It’s all simply currency to the crown, and her own personality or womanhood means very little in the grand scheme of things.

As the film points out at the very beginning, this is a “fable from a true story.” We have no idea what exactly went on those three days, especially what was going on inside Diana’s splintering mind, but “Spencer” gives us an idea of what it could have been, focusing exclusively on Diana’s story, for she is the most interesting and the one for whom we already have the most sympathy. We get a small glimpse of Princes William and Harry (Jack Nielen and Freddie Spry) as well as a few words from Charles (Jack Farthing), but the story remains laser-focused on Diana and particularly Stewart’s performance, with Larrain making sure she is given just the right amount of time in each scene to dive into the journey that becomes ever more clearly written on her face with each passing day.

There are times when the script seems out of sorts and missing a lot of the emotional impact it should have, instead relying on Stewart’s performance and the wonderful production and costume design for the heavy lifting and jumping from one moment to the next without much variation in context. Instead, everything is vague and left mostly on the emotional ride to get us to the end.

Overall, “Spencer” will stand out thanks to Stewart’s performance alone, propelling it to probably one of the best personifications of the late princess put to screen.

“Spencer”

117 minutes

Rated R for some language

3 stars