Now 89, Miss Jenkins published her first novel after graduating from Cambridge in the 1920s. Twenty-three works have followed, including biographies of Elizabeth the Great and Lady Caroline Lamb, as well as the haunting novel Harriet, now out of print.
In the 1980s Virago republished The Tortoise and the Hare. This 40-year-old novel is flawless. Jenkins doesn't shock and never advocates social change. Her world is peopled by upper-middle-class professionals with housekeepers. Gardens are sweeping and immaculate; children board at school. There are picnics by rivers, friends who lunch and trips to London to wander dreamily around galleries. Anyone faintly "progressive" - an architect with an open-plan house, a poetess who appears in Vogue - is gently mocked.
What marks Jenkins out is her perception and insight into character. In The Tortoise and the Hare there is very little action, and not even a traditional climax, yet the emotional journey travelled by the central character is extremely moving.
The lovely, romantic Imogen Gresham is in her thirties, married to the much older Evelyn. Dynamic, handsome, overbearing, Evelyn is a successful barrister who likes the good things in life. Imogen, who idealises her husband, seems motivated only by her desire to please him.
The book maps Imogen's incredulous and slow realisation that she no longer does. She has, in fact, lost Evelyn to her neighbour, Blanche Silcox. More surprising still, her rival is a dumpy 50-year-old spinster, who shoots and fishes, and lacks any taste in hats. She is Imogen's exact opposite and we start off, like our heroine, by feeling rather patronising towards her.
What a mistake. Seizing her last chance at passion, Blanche pursues Evelyn relentlessly, proving that the tortoise can always surprise the hare.
Readers may find Imogen maddeningly passive: she "just suffers", as her 11-year-old son comments with contempt. But Jenkins points out the unseen momentum in life which propels our acts - like leaves drifting downstream - by a seemingly "invisible force". Imogen can't swim against the current.
Of course, Imogen is partly culpable. With her head full of white geraniums and Wordsworth sonnets, she has never taken responsibility for herself. She fails to see the true state of her marriage or to understand what men desire in women.
While sympathetic towards her, Jenkins is strikingly even-handed. The author doesn't blame Evelyn. He needs the passion offered by Blanche (she has orgasms, Imogen doesn't) and prefers her grown-up, stimulating companionship to Imogen's fragile charm.
Imogen is abandoned by Evelyn but not by Jenkins, who gives the sad ending an unexpected twist. The Tortoise and the Hare also closes with the impractical Imogen acknowledging: "I must improve . . . There is a very great deal to be done." It's as if thi s positive note opens the door to the feminist fiction which has followed, where women faced with failing marriages and feelings of worthlessness learn to fight back, grasp the future and make something of their lives.