The shocker of the season finale of Downton Abbey, which aired in the U.S. last weekend, was the death of handsome, floppy-haired, formerly death-defying Downton heir Matthew Crawley. But a stranger moment played out in the scene before that, when Matthew joins Lady Mary in the hospital delivery room to cradle their newborn son. He vibrates with emotion; she radiates business. “We’ve done our duty,” she tells the love of her life, handing him the baby. “Downton is safe.”

Mary isn’t royalty, but her house always comes first. That bit of dialogue came back to me Tuesday morning, as two-time Booker Prize–winning novelist Hilary Mantel took heat from Prime Minister David Cameron and the English tabloids for remarks she made about the Duchess of Cambridge in an essay published in the London Review of Books. Kate is England’s most precious commodity, especially with Downton in hiatus, and the media stance on her is relentlessly positive. So when Mantel, in a piece titled “Royal Bodies,” suggested that Kate appears “precision-made, machine-made,” and wrote of royal persons that “at the most basic, they are breeding stock, collections of organs,” she was accused by the Sun and Daily Mail of attacking the defenseless Duchess. Cameron weighed in from India, where he was traveling, to say that Mantel’s comments were “completely misguided.”

Never mind that Mantel is dealing not in pronouncements but perceptions: her piece discusses not who Kate is (how could she know?) but what she seems to be. It’s an essay less about actual royals than the way they’ve been presented to us. And it travels from the coverage of Kate to the death of Diana to the discovery of the skeleton of Richard III to the possible blood type of Henry VIII, with a detour through a couple of Stevie Smith quotations and Mantel’s own encounter with the Queen. Which is to say, it’s a saturated, highly dexterous piece of writing, exactly the sort of thing that begs to be misinterpreted. But what’s strange about the tempest over it is that Mantel actually provides a compelling rationale for both the press’s and the public’s undeniable, salacious interest in Kate’s body. The Duchess’s ability to produce an heir is what ties her to monarchs past; it literally put her in line with them. This is, along with the real estate holdings, probably the most traditional aspect of the monarchy left. Without it, there is no monarchy. Why not point it out?

“In looking at royalty we are always looking at what is archaic, what is mysterious by its nature,” Mantel writes. Perhaps what ruffles the critics of her piece is that the woman lauded for her accounts of Tudor England brings that historian’s eye to a figure of our own time. Can you write about contemporary royals as if they are already consigned to history? Maybe the better question is: Is there any other way to write about them? In a sense, their distance from the trappings of regular life requires that approach. In Mantel’s version of Kate, her interior life is rendered even more remote than that of Anne Boleyn. There’s curiosity about what occupies her thoughts, but no presumption to know it. There’s no mention of her family. There’s no mention, even, of William. This would be more bothersome if it didn’t accord with mainstream coverage of Kate, which tends to focus exclusively on her clothing and weight and will soon shift to her maternity clothing and weight, followed almost certainly by her baby’s clothing and how quickly she loses her weight. Yet somehow that’s respectful, whereas Mantel’s ultimate argument — that we back off the royals, leave them to puzzle out their modern status at a cool, historical remove — registers as an attack.

We in the U.S. are not unfamiliar with the idea of one’s body being one’s duty, possibly even one’s destiny. This is Oscar week, culminating in our most concentrated public display of professional beauty and professional grooming. It’s a week when scores of our prettiest women — some who look (as Mantel might write) as if they’d been designed by a committee and built by craftsmen, and who bear (as Mantel might write) the strained smile of women who really want to tell reporters to bugger off — get asked who they’re wearing, as if they bear the carcasses of designers down the red carpet. Talent vies with wardrobe for attention, and increasingly, a baby bump trumps both. The House of Jolie-Pitt is not yet as historically significant as the House of Windsor. But the pregnant-celebrity industrial complex that Simon Dumenco wrote about on AdAge.com this week is hard at work convincing us that these bloodlines too must be cultivated and celebrated. It’s enough to make you nostalgic for a time when only real royal babies mattered.

In Bring Up the Bodies, Mantel describes the beheading of Anne Boleyn in a single, masterful stroke: “The body exsanguinates,” she writes — the blood spills from it and marks its passage from life to death. Of course, Anne’s blood had its revenge. Her daughter Elizabeth took the throne, outlasting and outmaneuvering her rivals, and led England through four decades of military and cultural glory.

What will Kate’s blood accomplish? Mantel opens her piece with the idea (prompted by an unwelcome interview question) of giving Kate a book called Queen of Fashion: What Marie Antoinette Wore to the Revolution. “It’s not that I think we’re heading for a revolution,” she writes. “It’s rather that I saw Kate becoming a jointed doll on which certain rags are hung. In those days she was a shop-window mannequin, with no personality of her own, entirely defined by what she wore. These days she is a mother-to-be, and draped in another set of threadbare attributions.” It would be interesting to know, her argument goes, whether the jointed doll would agree with that perception of her. It would be interesting to know what she makes of the role of fashion and fertility in the fortunes of queens before her, whether she sees any lessons that apply. Odds are slim that we’ll find out. But it doesn’t seem so misguided to wonder.