The Life and Loves of a She Devil is Fay Weldon’s most celebrated novel, the one that made her name and will ensure her literary legacy. When it was published in 1983, it licensed a generation of second-wave feminists to own their inner demon. “It affords a scintillating, mind-boggling, vicarious thrill for any reader who has ever fantasised about dishing out retribution for one wrong or another,” wrote New York Times reviewer Rosalyn Drexler. What Drexler described as “a remarkable tour de farce” has twice been adapted for the screen, first as an award-winning BBC serial, starring Julie T Wallace as a gloriously ungainly Ruth, and then as a film with Roseanne Barr reprising the role to rather less monumental effect.

Thirty-four years after igniting the reading world with her rage against the male of the species, the She Devil is back. Weldon’s lantern-jawed antiheroine is still married to the adulterous Bobo, now a senile shell of a man, and still lives in the tower she liberated from her rival, Mary Fisher, though for part of the new novel Mary lives there too – a spectral presence “woo-h woo-hing” her undying belief in the power of love.

“I am in my 80s now and I see no one fit to follow in my footsteps,” rants Ruth, now Lady Patchett, president and chief executive of the Institute for Gender Parity, in the novel’s opening sentence. With those words, we’re off into the wayward imagination of the UK’s most devilish novelist. “The timing was slightly difficult because I had to work out how old Ruth was,” says Weldon, who eventually figured out that, at the time of writing, she and her she devil must both be 84.

For decades, people have been urging her to write a sequel, so why now? “There didn’t seem to be any reason to do so until Germaine [Greer] got into trouble, as everyone does these days, for saying that just to get one’s genitals chopped off doesn’t make you a woman. And Jenni [Murray – presenter of Radio 4’s Woman’s Hour] has said if you haven’t been brought up a woman, you haven’t gone through that process and all the various slights that older women are accustomed to …”

The woman who utters these words smiles serenely from the end of her kitchen table as if nothing could be more obvious. She’s talking about the Terf – or “trans-exclusionary radical feminist” – wars that have been raging for several years now within feminism, and, being a congenital controversialist, Weldon obviously had to join the fray.

To meet Weldon is to gasp at her audacity, to wonder at her zest for occupying the frontline of sexual politics

The character on to whom she projects the dilemma in Death of a She Devil is Ruth’s estranged grandson Tyler, a beautiful boy who can only inherit the considerable family fortune if he agrees to become a beautiful girl. The villain of the piece is Valerie, a lesbian and “fourth wave feminist”, who – Weldon says – has therefore “always been on top literally and metaphorically”.

To meet Weldon is to gasp at her audacity, to wonder at her zest for occupying the frontline of sexual politics whether or not she has an investment in it, but also to admire her chutzpah, and the energy that has kept her turning out headline-grabbing novels into her ninth decade.

In the novel, Ruth observes her “awesomely handsome” post-operative grandchild at play. The online game she was playing, “according to its box, was Slaves of Blood and Savagery and in smaller font below: See girls struggle! See the blood flow! Have a laugh!!!” She concludes “testosterone would always win the battle over oestrogen … the old Adam would always rise again”.

Computer-gaming men, Weldon points out, often have women as avatars. “It’s more fashionable to be a woman. It seemed to me that women appear to be more powerful, at least among young men.”

It’s a concept that fits in very snugly with the theme of both The Life and Loves of a She Devil and its sequel – that the killer impulse, the one that gives Ruth her cosmic powers, and by implication is powering the Terf wars, is envy. Weldon is delighted by her own arrival at this understanding as we talk, and points out that she has only just started to speak publicly about the new novel. Envy is not the same as jealousy, she says. “The only thing you can do with envy is become the envied object.”

Meryl Streep, Ed Begley Jr and Roseanne Barr in the 1989 Weldon adaptation She-Devil.. Photograph: Snap/Rex Features

In the original novel, Ruth’s solution is to resort to drastic cosmetic surgery to become more like the object of her envy, the beautiful romantic novelist Mary Fisher. “You could see the terrible doom and depression in the early 80s, when women were supposed to be happy with what they had but they weren’t,” says Weldon. “The She Devil was noticing all this and was a size and a shape that was unfashionable. One became very aware that everything was about the prettiest women, and still is – in fact it’s more so now, because there are cameras everywhere.”

When she published She Devil, she was 52 years old and living the life of a bestselling novelist with her second husband, jazz musician turned antiques dealer Ron Weldon, and their sons, in a large north London house with her mother installed next door. Her mother was appalled at the choice of title, worrying that no one would ever take her seriously again. But Weldon was determined. It came, she says, from Frank Harris’s My Life and Loves, “which was the book I remembered most from my childhood”. (My Life and Loves was a privately published memoir of the Irish American writer’s sexual adventures, lavishly illustrated with drawings and photographs of nude women. It was finally made public in 1934, three years after Harris’s death, by the Paris-based Obelisk Press, which also published Henry Miller and Anaïs Nin.)

The childhood that might have led Weldon to such precocious reading is detailed in a memoir, Auto da Fay, published in 2002. It began in the womb, during a New Zealand earthquake in which her English mother – several months pregnant with her second child – was forced to take refuge on a sheep farm, not knowing whether her philandering GP husband was alive or dead. She named the new baby Franklin, because she had been expecting a boy. “Thus I started out in a state of ambivalence,” wrote Weldon. “I took out library books as Franklin and read them as Fay.”

After the marriage broke down, her mother earned a living writing romantic novels under the pen name of Pearl Bellairs, borrowed from Aldous Huxley’s novel Chrome Yellow. She sent her daughters off to a convent school where Weldon reported that she had pashes on girls and became fascinated by the mutilation of saints. “They were beautiful and good, and pain was their reward: I was fascinated and horrified.”

When the family came to the UK, Weldon won a scholarship to South Hampstead High School and went on to study psychology at St Andrews University. After a while odd-jobbing as a waitress and a hospital ward orderly, she landed a job in the Foreign Office propaganda unit, where she began her writing life penning pamphlets to be air-dropped on Poland as part of the cold war effort.

She left that job after becoming pregnant by a musician she met while he was moonlighting as a nightclub doorman, and deciding that she wanted the baby but not the father. After a period of living with her mother and sister in a “haunted” teashop in Saffron Waldon, she succumbed to marriage to a middle-aged headmaster who – according to her memoir – didn’t want sex with her but was happy to lend her out to other men.

Julie T Wallace in the TV adaptation of The Life and Loves of a She Devil in 1986. Photograph: BBC

This particularly startling section of the book offers two invaluable insights into the relationship between Weldon’s life and her literature. In Auto da Fay, the haunted teashop story is recounted as fact, so does she really believe in ghosts? “I believe in the folly of one’s own mind,” she parries. “Because I live in a haunted house isn’t to do with the house: one’s perception is different to the reality.”

While the haunting anecdote reflects the playfulness of Weldon’s attitude to facts – her sense of entitlement to tell whatever story she wishes – her account of her brief marriage to headmaster Ronald Bateman points to a different sort of evasiveness, gesturing at a reality so uncomfortable that she resorts to referring to herself in the third person, only returning to straightforward autobiography after she meets her second husband, Ron Weldon. “Poor Ronald Bateman,” she writes in Auto da Fay. Rather than blaming him, she berrates herself as “a heartless, practical monster”.

“My 20s were spent in a complete state of panic,” she says now. “For the first seven years, I was a zero contract worker with a baby and no husband and my mother trying to help. Then I went into advertising and worked from home, but it was juggle, juggle, juggle …”

Her advertising career has become the stuff of legend, with slogans ranging from “Vodka gets you drunker quicker” – turned down – to “Go to work on an egg”, which she has since said she didn’t actually write, though she was running the campaign that produced it. Her relationship with the Egg Marketing Board wasn’t always so successful: an attempt to get housewives of 1950s Britain to add an extra egg to their Christmas puddings backfired disastrously when she forgot to add sugar to the recipe.

If her memoir is full of tall stories, her novels are equally full of autobiographical insights. Life Force, published in 1992 as her marriage to Ron was breaking down, chronicled “the havoc that a man with a very big willy wreaked on a little circle of suburban women”.

We’re having an upheaval. Mothers try to be friends not parents, but children need boundaries

The split with Ron, after he left her for his psychotherapist, threw Weldon into a She Devilish rage with men and with therapy, which she vented loudly and publicly. She had been in analysis herself for 27 years, “because Ron was in it and he said: ‘You’d better go or you won’t understand a word I’m saying.’” ”The trouble began when he moved from analysis to therapy, she says. On one occasion she rang his therapist. “I said: ‘Can’t it please stop, because it would be nice to have a conversation that didn’t go through you.’ She said, ‘My dear, you’ll be sorry if it stops.’”

Her hatred of therapists was sublimated in her 1993 novel Affliction, though she says now: “I’m not as wholesalely against it as I was. It makes you much better on the radio because you’re used to putting your thoughts into words.”

Through all the tempests of her life, Weldon has continued to turn out books with a regularity that, she fears, has done no favours to her literary reputation: “If you’re too prolific people dismiss you as a wordaholic.” Thirty-four novels are listed in Death of a She Devil, along with seven short story collections, three children’s novels and six works of non-fiction, which range from a monograph on the writer Rebecca West to a polemic, What Makes Women Happy (“in this order: sex, food, friends, family, shopping, chocolate”, according to the introduction. “‘Love’ tends not to get a look in. Too unfashionable. Or else taken for granted”).

A near-death experience 12 years ago, when an allergic reaction briefly stopped her heart, has done nothing to slow her productivity. She teaches one day a week at Bath Spa University and combines her writing life with guest appearances at literary festivals – with the funds to pay for a taxi – within a 100-mile radius of the handsome townhouse in Dorset where she lives with her third husband Nick Fox, a poet and bookseller 15 years her junior, who now acts as her manager.

They have seven sons and a daughter between them who descend on them for high days and holidays, and it is through this beloved jumble of students, children and grandchildren that she keeps contact with the modern world. “Feminism,” she says, “was a successful revolution, but after a revolution you lose a generation. We’re having an upheaval, with women going out to work and children going to nurseries. Mothers try to be friends not parents, but children need boundaries, so it’s a kind of freefall. Child rearing has changed and it is producing another kind of person.”

One result of that change is Valerie – the fourth-generation feminist in Death of a She Devil, so convinced of the superiority of women that she doesn’t associate with men at all. Another is Tyler/Tayla, the product of a family so dysfunctional that he has pretty much had to raise himself. It’s a pantomime intervention in the gender queer debate, and there is a palpable sense of Weldon the mischief-maker once again buckling on her flak jacket. But in a way, she says, it’s quite a serious book. “One’s themes are serious and one doesn’t want to trivialise them.” It was ever thus.

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