WHAT WAS IT about England between the wars that accounts for its bumper crop of naughty girls - Vita Sackville-West, Violet Trefusis, Clare Sheridan, the Mitford sisters? And now comes Nancy Cunard - who may be the wildest and most flagrant of the lot - in an admirable biography by Anne Chisholm. One explanation, undoubtedly, was the aftermath of the first war, which wiped out a generation of young Englishmen and a social order and made it compulsory to topple old conventions. But some of these upper-class outlaws - and none more than Nancy Cunard - seem to have been driven by the simple need to shock their mothers.

For Nancy, striking out against her mother, Lady Cunard, became a way of life. Alas, Lady Cunard was a fast-moving target, hard to hit. Defiant of convention herself, she was the mistress of Sir Thomas Beecham for 30 years (and in deep middle age, changed her name from Maude to Emerald on "a sudden whim"). Lady Cunard took pride in serious conversation at her parties and she was erudite, witty and dedicated to the literary arts - which did not leave much room for poor Nancy, an aspiring poet, to stage a good rebellion. There was nothing for it but to rush to outer limits of conventional behavior and plunge right over. That became the story of her life.

Nancy's hostility towards her mother was legendary. Once at Windsor Castle they were "playing the game...of who they would like to see best come into the room and Nancy Cunard said in that high voice "Lady Cunard dead ."" So threatening was she by "the strong undertow of her mother's social life" that she fled London at 23. Later, she fled England. She lived abroad most of her adult life, always on the move from Paris to Normandy to Venice to Biarritz and back again.

The fierce precocious little girl became a fierce self-centered and willful young woman - arrogant, careless and, by all accounts, irresistible. An archetypal 1920s siren, she smoke and drank in public. William Carlos Williams met her in Paris in those early years and reported, "I never saw her drunk; I can imagine that she was never quite sober." So she had a certain "reputation." She also managed to develop her own unique style - an evanescent slimness, an untroubled gaze, a dancing walk. African bracelets of ivory, worn from wrist to elbow were her trademark. By the time she was in her mid-twenties, she already sounded, as Chisholm says, "like a novelist's invention." No wonder she was thought (erroneously) to be the model for Lady Brett Ashley in Ernest Hemingway's The Sun Also Rises. Nancy did, in fact, inspire an uncommon number of artistic works. One of her lovers, Michael Arlen, wrote her into The Green Hat as the heroine Iris Marsh and Piracy as Virginia Tracy, a woman of "glamour. But...[with] a rottenness in that glamour.... A queer provocative indifference there was about her." " Aldous Huxley, another lover, wrote her out of his system by putting her in Antic Hay as Myra Viveash and in other novels as the rich, beautiful, self-centered heroine. T. S. Eliot dropped into The Waste Land "a society girl who writes poetry...and sounds suspiciously like Nancy," but he was persuaded to pull her out again. (It was not a flattering portrait).

In common with her mother, Nancy enjoyed the company of people with creative talent which perhaps she felt she lacked. Her poetry was published, but it was considered labored. None other than Ezra Pound gave her critical advice: "Iambic pentameter is a snare," he cautioned, "because it constantly lets one in for dead phrases like "in this midnight hour"...Damn it all, midnight is midnight, it is not "this midnight hour."" "

In Paris, Nancy was naturally drawn to the revolutionary views of the Surrealists, one of whom, Louis Aragon, of course became her lover and introduced her to the politics of communism. Although she never officially joined up herself, having a "a Communist party member as a lover...was a wonderful tease for her mother."

Most of Nancy's behavior was designed to "tease" her mother - to drive her crazy, that is - but nothing hit the mark quite like her taking up with Henry Crowder, the black jazz musician from Washington, D.C. She saw him playing the piano in a Venice night club in 1928 and shortly sent a gondola to fetch him. Lady Cunard heard the news of their liaison from her rival, Lady Oxford, who breezed into lunch one day asking, ""Hello Maude, what is it now? - drink, drugs or niggers? "" Lady Cunard went into a rage. Nancy responded by writing a diatribe against racism and her mother (but mostly against her mother) entitled Black Man and White Ladyship and sending it to her mother's friends. It was an act of "literary matricide" for which society did not forgive her. Nancy and her mother never spoke again.

To Nancy, Henry Crowder was the most significant figure in her life. "Henry made me," she later said. Indeed, he sparked her interest in racial justice and inspired her one great work, the compilation of an anthology of black history, politics and culture called Negro.

Nancy revelled in fighting for a cause. She championed racial equality, the republican side in the Spanish Civil War and once considered taking up the plight of gondoliers in Venice. According to Chisholm she was generous, loyal and had a capacity for hard work.

But these commendable qualities seem pale and elusive compared to the dark side of her nature so vividly illustrated in this book. Nancy Cunard was capricious, erratic and self-absorbed. She pushed everything to its extreme - and then some. Sexually she was so indiscreet and undiscriminating as to make mere promiscuity seem like child's play. Early on, Henry Crowder was suprised to note that Nancy's chauffeur was "overfamiliar" to her, and then he realized the obvious reason why. Her friend Richard Aldington described her in a short story as ""a kind of erotic boa constrictor. She swallowed men whole. You could almost see their feet sticking out of her mouth."" Drinking was another pleasure she took to its extreme. She was, Chisholm suggests, probably an alcoholic for the last 30 years of her life. Eventually, descending into madness, she died alone in a public ward of a Paris hospital in March of 1965.

What a strange, unsympathetic woman - so complicated and bizarre it takes a first-rate, full biography like this to do her justice. CAPTION: Picture 1, Nancy Cunard by Cecil Beaton; Picture 2, Nancy Cunard by Curtis Moffet (circa 1927)