But that October evening in 1990, when the Booker judges announced their choice, changed everything. Possession also won the very lucrative Irish Times/Aer Lingus Prize; Byatt was made a CBE. She found herself one of the most talked-about writers not only in this country but around the world: there were prestigious foreign trips and conferences, saturation press coverage. Suddenly, she was everywhere, and not just on paper - judging the Best of Young British Writers; working with Patsy Kensit on the film of Angels and Insects; debating her Matisse Stories with art historians; launching herself into the row about Martin Amis's advance with the now famous remark about "male turkeycocking".
Two weeks ago the BBC devoted a Bookmark programme to her, in anticipation of her new novel, due next month. Babel Tower is her first "big" book since Possession - although in between have come Angels and Insects and two books of stories. In the new book Byatt leaves behind the Victorian world she has haunted in recent work, and moves her action to Sixties England.
Antonia Byatt seems to have found a new confidence. A powerful presence in her public appearances, she certainly has no shyness about the weight of her intellect, but it is as if she no longer has anything to prove either. She can indulge the popular touch, and her playfulness. Speaking at the Tate Gallery after The Matisse Stories came out, she replied to a fairly solemn art-historical question about the artist's influence by talking about the colours of the cushion covers she'd just bought for her house in France. No one with lesser academic credentials would have dared such a cosy answer.
THE BBC programme took Byatt back to the scenes of her northern childhood; there were tears in her eyes as she revisited her old school, the Quaker School in York. Born in 1936, she was the eldest of four talented children in a puritan, high-achieving and competitive family. Their father, a county court judge, was away a lot; their mother, a former teacher, is remembered by Margaret Drabble as deeply depressed and frustrated by domestic life. Byatt's third novel, The Virgin in the Garden (1978), carries vivid memories of a subdued and bleak wartime childhood. Cambridge, where she went to Newnham College, must have come as an escape and a relief: her work is full of people who find refuge in academic pursuits. Her university career was brilliant: a First, followed by research at Bryn Mawr and Somerville.
She married in 1959, and had two children with her first husband Ian Byatt. The marriage lasted 10 years, after which Byatt remarried and had two more children. A tragedy occurred in 1972, when her son Charles was killed in a road accident at the age of 11. She has been married to her second husband, Peter Duffy, a businessman, for more than 25 years. They have a home in south-west London.
At the beginning of the Sixties, though, she found herself with two young children suddenly a prisoner, as her mother had been, of domestic drudgery. The strains of combining domestic life and fulfilling work have always figured in her work, but she went back to the academic world in 1962, to teach at the University of London. From 1965-69 she lectured at the Central School of Art and Design, and again at University College London for many years, until the Eighties.
In 1963 the rivalry with her younger sister Margaret Drabble hit the public eye - although they have both said it dates from childhood days - when Drabble published her first novel, A Summer Bird Cage. Its subject? The competition and animosity between two clever sisters. It was an immediate success, and while Antonia was washing nappies, pursuing an academic career and desperately trying to complete her own first novel (typically, her younger sister had beaten her to it; Byatt's was published a year later) Margaret was rapidly becoming one of the darlings of Sixties literary life.
A couple of moments in the Bookmark programme said it all. Shot one: Byatt at work in the British Library, in shapeless clothes and bottle- glass specs; shot two: Margaret Drabble, sleek and glowing, prancing in miniskirt for the cameras in some hip Sixties room.
Byatt hit back with her own 1967 novel, The Game. It is the story of - yes, two sisters; Cassandra, the Oxford don and Julia the bestselling novelist. Always a brilliant observer of details, Byatt describes their footwear when the sisters meet for the first time for several years on a visit home: Cassandra is wearing "a pair of those shoes affected by women dons, cubanheeled, punched, laced, high in the instep"; Julia is wearing knee-high black boots with tassels swinging from the cuff. The book contains intense adult rivalries and vicious childhood games - at one point the sisters fight with "nails, teeth, shoes, silently intent on real damage". It ends miserably when Julia cruelly caricatures Cassandra in a book and Cassandra gasses herself. After this, Byatt published no more fiction for a decade.
Antonia Byatt has always been such a high achiever - there were studies of Iris Murdoch, and of Wordsworth and Coleridge, as well as the fiction writing, teaching and family life - that it is hard to imagine her in awe of anyone else's achievement, even a younger sister's. And why should we still care about this old business? Well, it is a story of the Sixties, the decade in which Byatt has set her new book, a decade that was not kind to Byatt the writer, that preferred Drabble's taut, lightly-spun style to her sister's high moral seriousness.
Seriousness has always been Byatt's problem - until, with Possession, she learnt how to turn it into an asset. Before that, it put her at odds with the whole tradition of post-war British fiction, for which the ticket was written largely by Kingsley Amis. Her books, laced with symbolic patterns and moral and intellectual debate, could hardly be further from Amis's recipe for laconic, middle-brow comedy, whose favourite target was "pretentious" and serious people - especially women. Byatt's 1985 novel Still Life, set in the Fifties, introduces Kingsley Amis as a character. The young Frederica Potter, "doomed to be intelligent", feels "a very simple sexual distaste for Lucky Jim" and Byatt (under cover of her heroine) gives its author, and in particular his attitude to being serious, and to "nice and nasty skirts", a going-over. This might be seen as background to Byatt's recent comments about Amis fils.
So how did this high-minded academic, at odds with the contemporary book world, transform herself into a Nineties bestseller? How did she marry seriousness with the middlebrow? In the Independent in 1995, she wrote about the genesis of Possession, and the influence of Umberto Eco's Name of the Rose, "which combines medieval theology, church history, gleefully bloodthirsty horrors, reflections on the form of the novel, with a hero who is an avatar or precursor of Sherlock Holmes...". Eco seemed to point the way. "I half-knew that the form of my novel should be a parody of every possible form, popular and 'high culture'..."; romance could co- exist with history; popular fiction with academe. The modern Byatt was made. Readers responded to the popular, but appreciated the serious: Fay Weldon wrote that "it's such a relief to be taken seriously as a reader".
Byatt become a bestseller, but she also changed in other ways. She could, for instance, write a story in The Djinn in the Nightingale's Eye, published last year, that described a stout middle-aged academic at a conference in Istanbul having prolonged, magical and lyrically described sex with a huge and scaly Turkish genie with "yellow horny toenails". Afterwards, she crams him back into his bottle and takes him home to Primrose Hill.
Jonathan Burham, Byatt's publisher at Chatto & Windus, thinks there has always been "a strand in Antonia's work that is deeply erotic" but also sees a new "flood of sensuality" as she relaxes in the glow of success. Angels and Insects, for all its 19th-century setting and passion for bugs, has some daring sexual writing; The Matisse Stories are more sensual than sexual, with Byatt revelling in sheer colour, but it's typical of the new Byatt to celebrate this outpouring of voluptuous pinks and creams, maroons and blues, and to place them in an ordinary local hairdressers. She has learnt to mingle the brainy critical self of her years as a lecturer at Central School of Art with the world of women's mags. There is also a powerful, if slightly weird eroticism in her new novel Babel Tower: it contains a book-inside-a-book, called "Babbletower", which is prosecuted for obscenity. Unkind readers will note that babble rhymes with Drabble.
A S Byatt may have changed, but it's also true that literary fashion - as strange and fickle as fashion in any other realm - has moved to meet her. Her obsessions have become ours. The world is mad for Jane Austen and period fiction: she is already "possessed" by the 19th century and its ways with words. Science is in literary vogue - Angels and Insects is there to greet it. How timely, we might think - but if we look back to The Game of 1967 we find her heroine in love with a television naturalist enthusing about snakes. And even those high-laced shoes "affected by women dons" eventually came back into style.Reuse content