Eyes dilated, lips parted, wild hair, head thrown back and clothing awry, a woman is swaying and undulating, seemingly in the throes of a crazed trance. Or maybe she’s drunk, drugged, or in terrible pain? This is our first full sight of my great-aunt and namesake Virginia Woolf, played by Elizabeth Debicki in a new film, Vita & Virginia, written and directed by Chanya Button and, where accuracy is concerned, it sets the tone for the movie.

Vita & Virginia tells the story of the relationship between two 20th-century literary celebrities — Woolf and Vita Sackville-West. The bare facts are these: their love affair took off in 1925 when Virginia, a respected author, was 43, and Vita, a more popular novelist, was ten years younger; both were married. But whereas Virginia was sexually timid, Vita was voraciously carnal — and scandalous — having caused mayhem in 1919 by running off, disguised as a man, with the society beauty Violet Trefusis.

The divergence between them was also social. Virginia leant to the intellectual aristocracy and the terraced townhouses and bohemianism of Bloomsbury, whereas Vita, whose roots were in England’s landed nobility, had grown up at Knole, a vast sprawling Elizabethan mansion. Her pedigree was part of the fascination for Virginia and in 1928, after their passion had waned, would provide the material for Woolf’s extraordinary transgender adventure Orlando, a novel in which the hero becomes a woman.

But whereas Virginia was sexually timid, Vita was voraciously carnal — and scandalous.

Film dramas that reimagine real-life historical episodes are a respectable genre. Shakespeare in Love, Lincoln, The Happy Prince, Colette and most recently The Favourite and Tolkien are a few that fall into this category. We go to them not for information about the past, but for entertainment, great acting and the sumptuousness of period drama. We also seek that meaningful, if intangible, “something” that can only be conveyed by a fine script. Simplification, even slipshod research and downright falsehood, can be forgiven if we feel we are in the presence of a greater truth, and if the fictionalised version is powerful enough to touch something deep inside us.

So how does Vita & Virginia measure up on these criteria? Let’s start with the accuracy. Where this is concerned, any film-maker exploring Woolf-land is walking on ice. Bloomsbury is public property and there are multitudes of self-appointed guardians, both amateur and academic, who feel a much greater ownership of Woolf and her group than I do.

The Bloomsbury Grope

Hands up, I never met Vita or Virginia, who drowned herself in 1941. But Vita died in 1962, so there are many people alive today, including her grandchildren, who did know her. My father, Quentin Bell, was Virginia’s devoted nephew and biographer; my mother, Anne Olivier Bell, edited Virginia’s diaries. I knew several of the individuals who appear in the film: Leonard Woolf, Vanessa and Clive Bell, and Duncan Grant. I’m saturated in Bloomsbury and, although this probably makes it harder to judge the film’s artistic qualities, I am in a position to set the record straight on verisimilitude.

“We prepared really carefully — trawling over Virginia Woolf’s diaries, letters, her texts,” Button says. “[Debicki’s] performance is a blend of really meticulous research and her own response to the script and the character.” Two years ago I was sent Button’s script. It contained many errors and she and I discussed ways in which her version of events could be fixed. Then things went largely quiet. I waited with some misgivings to see what would emerge.

Vita & Virginia is a fact-based story that relies on its two lead actresses. They have to look the part. And here we run into difficulties. The slender and willowy Debicki, as Virginia, towers over Gemma Arterton’s petite Vita. The opposite was the case, with the real Vita a statuesque 6ft in height, while Virginia stood at 5ft 7in. The discrepancy could have been fudged with camerawork, but Button’s framing emphasises it. I felt for Arterton as she craned to kiss her lofty lover in a way that must have given her a pain in the neck.

Woolf and Sackville-West in 1933.

Then there’s Grant and my grandmother, Vanessa Bell. Both play prominent supporting roles. But what happened here? The real Bell wore her hair swept up and had a grave and monumental beauty, while the real Grant was agreed to be startlingly handsome (and clean-shaven). In the film we are shown a strapping lass in a smock with loose, blond, pre-Raphaelite locks, alongside a camp ninny with a toothbrush moustache wearing something resembling a Marks & Spencer cardigan.

Indeed, the costumes often jar. We know that Virginia struggled with a faltering taste in clothes. But here she’s shown sashaying around, grandiose and soignée in modish 1930s geometrics, or floating across the twilit courtyard at Knole in a frilly nightie with bouffant blond hair cascading in coiffed waves: Ophelia meets Jerry Hall. By contrast, Vita wears tweeds or deluxe devoré velvets, opulent furs, oyster satin and a strikingly incongruous cerise animal-print coat. The film shows her arriving in an open-top limousine to drive her inamorata down to Knole. But Vita was not fabulously wealthy. She had been excluded from her inheritance and her finances were always in flux.

A camp ninny with a toothbrush moustache wearing something resembling a Marks & Spencer cardigan.

The average filmgoer will sit back and enjoy the lavish costumes and props without caring how wrong they are. But when you are as steeped in the subject as I am, the frequency with which such mistakes pop up becomes a torment. After a while I felt as if I had been punched around the head by fallacies and anachronisms.

Take the locations. In the late 1920s Vita and her husband, Harold Nicolson, were living at Long Barn, a pretty Wealden farm building with low-beamed interiors that the Nicolsons had converted. Instead, an austere grey Georgian mansion with pilasters purports to be their country home. Meanwhile, the impecunious Bloomsberries eat in the kitchen of an architecturally whimsical rural retreat posing as Charleston. “No,” I want to scream, “it was a farmhouse. And no, they didn’t eat in the kitchen!”

What about the design? Surely Virginia’s famously beautiful italic-inspired handwriting could have been recreated? But this clumsy, cursive script bears little resemblance to it. The improbabilities accumulate. They include an inconceivable scene in which Vita — through a conversation with her mother, Lady Sackville — tells the audience the story of her scandalous liaison with Violet in the presence of her two young sons, then aged 12 and 9.

Mrs. Dulloway

Again and again such annoyances butt in. Knowing that the film had a tight budget doesn’t make them easier to tolerate. There’s a sequence that tries to reconstruct the occasion when a group, including Virginia and Vita, travelled to Yorkshire to view the solar eclipse of 1927 — an episode recorded in one of Virginia’s most famous diary entries. She describes the crowds gathering on the moor and the eerie changes of colour that take place as the sun is cloaked and uncloaked. It’s a marvellous piece of observational writing. But Button, it seems, has instructed Virginia to gaze besottedly at Vita throughout. The script directions read: “She cares nothing for the spectacle they came to witness, when Vita is in her company.” Apart from the lovebirds and their group, the moorland appears deserted.

Button has located a recording of Virginia speaking, and Debicki has clearly listened to it. The outcome is an attempt to disinter a voice from the past — but, instead of Virginia’s resonant timbre and musicality, we get a posh squawk, mechanically mimicked from the original.

So does the drama offer riches enough for us to overlook the inaccuracies? For me, Vita & Virginia has deeper problems than houses and hairstyles.

My father used to tell a story that has stayed with me. He and my grandfather, Clive Bell, were at Charleston one rainy afternoon with little to alleviate the isolation in that remote farmhouse.

“If you could choose anyone to walk up the drive now, who would it be?” Quentin asked. No second thoughts about that; the answer came back: “VIRGINIA!” Virginia was fun. For her friends she made life seem like a party. The real Virginia wrote letters to her lover that are flirtatious and witty, and Vita’s replies are equally frisky and joyful.

Sackville-West’s desk in her writing room in the tower at Sissinghurst Castle Garden, near Cranbrook, Kent.

This film favours a different Virginia, one who is pensive and introverted. This Virginia is given to occasional gnomic utterances. At moments of mental crisis Button introduces flocks of CGI crows and triffids germinating from between the floorboards, and she films Debicki staring ominously at the lapping waters of the Thames. Here is a “mad” prodigy, trembling with hypersensitivity and hurling crumpled-up pages of manuscript into the wastepaper basket.

Button gives her lead actresses pieces to camera in which they speak the words of their real-life correspondence. The film borrows from those immortal diaries and letters made available to the world by my mother, and Vita’s son, Nigel Nicolson. Unfortunately this touch of authenticity backfires. The film’s characters talk like books, not real people. On the page, their epistolary exchanges live vividly. For me, delivered to camera, they wither and die.

A “mad” prodigy, trembling with hypersensitivity and hurling crumpled-up pages of manuscript into the wastepaper basket.

Button’s Virginia is not the flesh-and-blood Virginia my father longed to see walking up the drive. This one seems to have been lifted unmediated from her writings, and there is scarcely the flicker of a smile on Debicki’s features. Button claims that Debicki had “an instinctive understanding of the character”. She should have added, “the character in the script” — to distinguish her Woolf from the real Woolf.

But Button says: “The relationship between Vita and Virginia that we depict in the film is absolutely one that they had … People have loved each other in all different ways, shapes and forms for all time, so it doesn’t really feel out of place to me that there was an LGBTQ story that we’re looking at in history…”

Button wants us to understand, I think, that these women’s lesbian love — unconventional for its time — is transcendent. It is a worthy subject for drama, first explored by Eileen Atkins 26 years ago in her stage play of the same name, which was also the starting point for the movie version.

A Brand of Her Own

And yet the topic of lesbianism has been so well aired on screen that it’s hard not to ask what this film has to add. Or are we witnessing the growing tendency to piggyback on celebrity that seems to cast a flattering lustre on film-maker and audience? Isn’t there something bulletproof about choosing to adopt Woolf as the vehicle for a commentary on LGBTQ? She was certainly a genius, but has become a top brand. And top brands are great for product endorsements.

So does Vita & Virginia have that intangible “something”, that greater truth? Audiences will have to reach their own judgment — but, for me, no.

Despite that, I wish I could issue a health warning to future screenwriters and directors of films about my great-aunt — and there will be others. It is that films send out powerful messages. If you want to tell the world about a transcendent lesbian relationship, go ahead. Be brave, tell it without leaning on the crutches of dodgy research and biography, let it take wing. Misrepresenting Queen Anne in The Favourite is one thing. She lived 300 years ago. Misrepresenting people whose lives intersect with living memory is another.

I have some sympathy with the family of JRR Tolkien, who were so offended by Tolkien’s inaccuracies that they published a strongly worded statement disclaiming it. For audiences of Vita & Virginia will not only leave the cinema oblivious to the manifold complexities of the real-life protagonists, but will also take away a version that will tarnish future understanding of those characters.

Still, one thing is comforting. Woolf’s written words will outlast those of Chanya Button.

Virginia Nicholson is a writer and the daughter of Woolf’s nephew and biographer, Quentin Bell