The Bloomsbury Ballerina, By Judith Mackrell

Maynard Keynes's eccentric Russian wife wowed audiences and appalled Virginia

Lydia Lopokova could hardly dance the part of the soubrette in Les Femmes de bonne humeur because, she confessed: "I laugh so much." The delight and comic energy she brought to this 1917 Ballets Russes production was what made her, for a time, the most popular ballerina in Britain. Fans chanted her name during performances; 300 people would queue for return tickets. Yet, as Judith Mackrell relates, Lydia danced herself out of the limelight. The Diaghilev protégée who had dueted with Nijinksy and twirled as a child before the Tsar became a forgotten star.

"Little Pet" or "Loppie" (as Lydia was nicknamed by doting fans) was never a classical romantic lead, but the diminutive Russian was strong and swift on stage. Spanish journalists once asked to inspect her costume, incredulous that she could leap so high without wires. Beguilingly expressive, Lydia danced with her eyes and lips.

Stravinsky was her lover, Eric Satie sent her flowers, Picasso drew her and Gabriele D'Annunzio wanted to "write a dance" for her "eloquent" legs. But it was the brilliant and homosexual economist John Maynard Keynes whom she utterly bewitched, despite his initial misgivings that she was "a rotten dancer – she has such a stiff bottom".

Lydia ousted his male lover and then wed Keynes despite the witchy froideur of his Bloombury circle. Lytton Strachey may have dubbed Lydia a "half-witted canary", with Clive Bell bitching that her "spiritual home" was Woolworths, but the odd couple remained devoted. Lopokova quit the stage when her husband fell ill and needed nursing on his various war-related missions to America. Surviving him by 35 years, she became a recluse in their Sussex farmhouse. Babushka-like in head-scarves and layers of jumpers, Lopokova occupied one room surrounded by clutter and cats, selling the odd Degas to pay for roof repairs and dining from tins well past their sell-by dates.

As Mackrell reveals, it was the kind of disappearing act Lopokova spent decades practicing. Twice the ballerina had "vanished" – possibly due to a mental breakdown or an unwanted pregnancy. As a young dancer touring the USA, Lydia had grasped the power of publicity, knowing when to play the exotic ingénue enchanted with all things American, and when to cover her tracks. Certain aspects of her life she wouldn't want exposed to public scrutiny: a bigamous marriage, an elopement with a mysterious Russian general. Lydia mastered the skill of being simultaneously extrovert and private.

Born in 1891 to a theatre usher of peasant stock and an Estonian masseuse with Scottish ancestors, Lydia entered St Petersburg's Imperial Theatre School aged ten. She left her homeland an ambitious teenager, returning 15 years later as a visitor. Her experience of the avant-garde with Ballets Russes, where she could be performing to Poulenc's scores in designs by Picasso and librettos by Cocteau, was balanced by years of dispiriting drudgery as a "toe dancer" in America. Stuck in vaudeville, her rigorous Imperial technique was showcased alongside acrobats and performing dogs. Yet, whatever the repertoire, Lydia managed to create laughter and high spirits.

She could behave badly, silencing a room with her observations on lesbian sex or by deliberately mixing up "aviary" and "ovary". Even in her fifties, she was recounting erotic dreams to the Canadian High Commissioner and a day later extracting a key which, she explained, she had hidden "for safety between my little bosoms".

With what Virginia Woolf termed her "genius of personality", Lydia inspired the character of Rezia in Mrs Dalloway. She afforded Woolf much malicious amusement, whether by chucking a used sanitary towel into an empty fire grate or exchanging headdresses with Beatrice Webb. "Lydia has the soul of a squirrel", Woolf smirked. "I assure you it's tragic to see her sitting down to King Lear."

Some of the disdain, however, wasn't undeserved. Lydia would play to the gallery and, for example, interrupt a serious discussion by insisting everyone look while she put a frog in a tree. Sometimes Mackrell herself finds it "hard to judge" Lydia's "exact degree of duplicity" in the lachrymose letters she fired off to employers or her mish-mashed Russian and English in newspaper interviews. Her dancing idiosyncrasies could seem contrived. Lydia would pirouette onto the boards, shoe-ribbon flapping, and once even flung her trailing underwear into the wings with a knowing grin. The English audiences loved this sort of reverse narcissism, although in private life Lady Keynes's chaotic disregard for appearances was greeted with dismay.

Mackrell spices her narrative with anecdotes and offers sympathetic insights with just the right amount of technical detail. By the time she died aged 89, her mind having wandered, her speech having reverted to Russian, Lydia was just a dance footnote. Mackrell has done an excellent job of putting her back in the spotlight again.