The Bolter, by Frances Osborne

Idina Sackville admitted she couldn't "bear goodbyes even on the telephone". Running away was something she made a habit of, like "the Bolter" in Nancy Mitford's The Pursuit of Love. As early as 1897, Idina had a blueprint for what to do if you could no longer abide your partner. Her father, Earl De La Warr, absconded with a can-can dancer. Three years later her mother, a socialist and suffragist, braved ostracism and divorced him.

Chinless and with tawny hair, Idina wasn't a looker. But clad in Molyneux with her black Pekinese "Satan" stuffed under one arm, she fizzed sexually. Married five times, Idina enjoyed countless lovers and ended up with a tattooed sailor called Jimmy. Now her great-grand-daughter has written an account of her life.

Frances Osborne, wife of the shadow chancellor, was unaware of their connection until she was 13. Even in the 1980s, great-granny was regarded as too scandalous to acknowledge. She had abandoned two sons from one marriage; her daughter from another was dumped with Idina's sister. Her hedonism found the perfect outlet in Happy Valley with its drink, drugs and promiscuity. Living luxuriously in Kenya, the white settlers ranged from the dissipated to the deranged. Idina was their "high priestess".

Variously described as "frail and fragile", "spoilt and vicious" and "a nymphomaniac", Idina did not "mirror the exploits of her generation... [she] magnified them". She wedded Osborne's great-grandfather, Euan Wallace, when they were barely out of their teens. Rich and handsome, he seemed a perfect catch. However, the First World War and Euan's infatuation with glacial architect's daughter Barbie Lutyens took their toll.

She left Euan, forfeiting her children and decamping to Kenya with husband number two. Barefoot and blissful, she showed a talent for dairy-farming but none for matrimony. She divorced again. In London, Idina inspired Michael Arlen's heroine in his bestseller The Green Hat. It wasn't long before the 30-year-old found a new Mr Wrong in the penniless womaniser, 22-year-old Josslyn Hay (later Earl of Erroll and victim of the Happy Valley murder case). Back in Kenya, Idina received guests in her green onyx bath and devised party games where guests swapped sexual partners. Two further marriages followed, to a white hunter and a pilot. Idina's only enduring love affair was with Africa.

She left few letters and no diaries. Sometimes the material feels thin, and reads like a romantic historical novel. Osborne is an imaginative scene-painter, but when describing war-time Paris she might have resisted the "petites rues" and "assiettes pour les croissants" tossed in to show we are in France. Idina wasn't admirable, but Osborne makes us sympathise with her. Finally reunited with her adult sons, she suffered a breakdown when both died in the Second World War. Idina confessed, "I'm not very brave anymore". These were goodbyes there was no bolting from.