She was irresistible. She inspired fiction, fantasy, legend, and art.

Some say she was “the Bolter” of Nancy Mitford’s novel The Pursuit of Love. She “played” Iris Storm in Michael Arlen’s celebrated novel about fashionable London’s lost generation, The Green Hat , and Greta Garbo played her in A Woman of Affairs, the movie made from Arlen’s book. She was painted by Orpen; photographed by Beaton; she was the model for Molyneaux’s slinky wraparound dresses that became the look fo the age—the Jazz Age.

Though not conventionally beautiful (she had a “shot-away chin”), Idina Sackville dazzled men and women alike, and made a habit of marrying whenever she fell in love—five husbands in all and lovers without number.

Hers was the age of bolters, and Idina was the most celebrated of them all.

Her father was the eighth Earl De La Warr. In a society that valued the antiquity of families and their money, hers was as old as a British family could be (eight hundred years earlier they had followed William the Conqueror from Normandy and been given enough land to live on forever . . . another ancestor, Lord De La Warr, rescued the starving Jamestown colonists in 1610, became governor of Virginia, and gave his name to the state of Delaware). Her mother’s money came from “trade”; Idina’s maternal grandfather had employed more men (85,000) than the British army and built one third of the world’s railroads.

Idina’s first husband was a dazzling cavalry officer, one of the youngest, richest, and best-looking of the available bachelors, with “two million in cash.” They had a seven-story pied-à-terre on Connaught Place overlooking Marble Arch and Hyde Park, as well as three estates in Scotland. Idina had everything in place for a magnificent life, until the assassination of Archduke Franz Ferdinand caused the newlyweds’ world—the world they’d assumed would last forever—to collapse in less than a year.

Like Mitford’s Bolter, young Idina Sackville left her husband and children. But in truth it was her husband who wrecked their marriage, making Idina more a boltee than a bolter. Soon she found a lover of her own—the first of many—and plunged into a Jazz Age haze of morphine. She became a full-blown flapper, driving about London in her Hispano-Suiza, and pusing the boundaries of behavior to the breaking point. British society amy have adored eccentrics whose differences celebrated the values they cherished, but it did not embrace those who upset the order of things. And in 1918, just after the Armistice was signed, Idina Sackville bolted from her life in England and, setting out with her second husband, headed for Mombasa, in search of new adventure.

Frances Osborne deftly tells the tale of her great-grandmother using Idina’s never-before-seen letters; the diaries of Idina’s first husband, Euan Wallace; and stories from family members. Osborne follows Idina from the champagne breakfasts and thé dansants of lost-generation England to the foothills of Kenya’s Aberdare moutnains and the wild abandon of her role in Kenya’s disintegration postwar upper-class life. A parade of lovers, a murdered husband, chaos everywhere—as her madcap world of excess darkened and crumbled around her.