PROFILE: Lady Antonia Fraser

Others wonder what has been omitted from Fraser's account of her "blissful" 34 years with the Nobel prize-winning playwright, a man famous for his irascible nature yet portrayed as a gentle soul given to self-parody and composing love ditties. The affair began in 1975 and Craig Brown, the columnist, wickedly ventured a comparison between the pair and the bickering television characters Basil and Sybil Fawlty, who made their debut the same year.

By Fraser's account, her husband and VS Naipaul, the writer, were bosom buddies with much in common - "they discuss anger like one might discuss a taste for port". Yet, according to The World Is What It Is, Patrick French's authorised biography of Naipaul, the latter thought Pinter's work adolescent, concerned with "childish fears and sexual longings". After Pinter offended the author by rejecting a nut loaf made by Naipaul's wife, Pat, the invitation to the couple's Wiltshire home "was never repeated", French wrote.

As Fraser's diaries reveal, there were plenty of friends to fall back on - Tom (Stoppard), John (Gielgud), Ralph (Richardson), Joanna (Lumley), Betty (Bacall) and Salman (Rushdie), who moved in with his charming bodyguards. Not to mention Jesse Jackson, the American civil rights campaigner: "Naturally he was incredibly pleased to meet Harold and me - we got the impression that it made his day."

There is more than a dash of Barbara Cartland, whom Fraser worshipped as a teenager, in the rendering of this traumatic tale. Within months of meeting Pinter, Fraser left her husband, Sir Hugh Fraser, the late Conservative MP, continuing the affair until she married Pinter in 1980, the year he divorced Vivien Merchant, his wife. Merchant never overcame the loss of her husband and drank herself to death in 1982. Their only child, Daniel, stopped talking to his father 15 years before Pinter died from cancer, aged 78, on Christmas Eve 2008.

Three months into the affair, Sir Hugh had asked his wife if she was in love with another man. "Yes! I am madly in love with someone else," she declared. When she identified Pinter, he said grimly: "The best living playwright. Very suitable." She "admired" her husband for "his essential decency and kindness", though not his "lack of emotional intimacy". But as she confessed, she had always wanted a genius. She even gave Pinter a mug printed with the words: "You are a genius". Besides, she writes, "the truth is that Harold has mesmerised me". Four years after Fraser married Pinter, Sir Hugh died of lung cancer.

The fallout continues to this day. Fraser's children are reported to be upset that their mother has chosen to expose old family wounds in a book that makes little mention of Sir Hugh. One family member said: "It is not very nice to see your father dismissed in a few lines and to go on about Pinter as this great romantic lover."

Fraser had apparently little pressing financial need to write these revealing memoirs. Pinter left her the bulk of his estate, an estimated £4.3m. How times have changed. Before she achieved fame, Fraser kept money on a tight rein and her children at a distance as she gave priority to her writing. Flora, her second child, recalled last year: "When she was working, the door would be firmly shut. More often than not you would hear her typing away, and when you heard that, you knew you couldn't disturb her, and you certainly didn't ask for pocket money."

Despite the froth that tops Must You Go? - which one wag renamed Must You Gush? - some detect a gritty integrity in this description of living and loving through adversity. To her admirers, Fraser's intellect and abilities are underestimated - obscured by the pink bee-sting lips and "debutante deportment" of a striking woman sometimes compared to Lady Penelope, the well-bred heroine of the Thunderbirds puppet series.

In her heyday she was lampooned as Lady Magnesia Freelove by Private Eye, and linked romantically to the former King Constantine of Greece, Rupert Lycett Green, Lord Lambton and Jonathan Aitken, who eulogised Fraser as a "Lady Madonna of the tennis courts".

She always declined to comment on these reported liaisons - she was married to Sir Hugh at the time - although in her memoirs she admits to "romances". However, she firmly denied spurning Clive James with the put-down that she slept only with the first XI.

She has lived in a large house in west London's fashionable Holland Park almost continually since she married Hugh Fraser in 1956. In 1977, when Pinter moved in after her divorce, he wrote in a mews house at the bottom of the garden. Fraser continues to write in her "eyrie" at the top of the house.

The Pinters' political beliefs underwent some dramatic switches. Fraser voted for Margaret Thatcher for "feminist reasons", but then came to abhor the Tories while they were in power. She and Pinter formed the June 20 Group, a gathering of literary types - including John and Penny Mortimer - to challenge the government. She voted Labour in 2001 and warmed to Cherie Blair before she joined Pinter in railing against Tony Blair's decision to invade Iraq in 2003.

The eldest of eight children, Fraser was born into an intellectual family of Catholic converts. She was brought up in Oxford, where her father, Frank Pakenham, who later became Lord Longford, taught politics at Christ Church. Her mother, Elizabeth, a great-niece of the Tory radical Joseph Chamberlain, became a distinguished biographer.

Despite the competition around her, Fraser cut an early dash. "She dazzled us all since the moment she could speak," her mother recalled. A fearless tomboy, at the age of three she is said to have spotted a viper in the garden sandpit and dispatched it with a spade. At eight she went to the Dragon school in Oxford, where she was "intensely happy" and played rugby for the school. Next came a Church of England girls' boarding school, which was not so good: "I was really a boy. I was way ahead of everybody in work and way behind emotionally and nobody wanted to walk with me."

Her happiness was rekindled at a Catholic convent, St Mary's at Ascot, where she "found the world of nuns frightfully interesting". Such was her self-assurance that when she went to Lady Margaret Hall, Oxford, to read history, she did little more than enjoy herself, earning a reputation for being "radiant and eccentric", with a penchant for cigars.

She got a job in publishing and at 23 married Sir Hugh. The couple shared duties in minding their growing band of children, but occasionally Antonia's independent spirit asserted itself. In 1963, when her fourth child was born, she took flying lessons, and the following year she went on an expedition through Ethiopia. "All my life I had secretly wanted to be the first white woman to tread somewhere or other," she recalled.

It was not until 1969 that she made her name with Mary Queen of Scots, an instant bestseller whose success "stunned" its author. Flora remembered the occasion because she was handed a £1 note for her pocket money with the words: "Keep the change."

Fraser had been married for 19 years and had six children when she ran off with Pinter. Her fateful encounter with the playwright was at a dinner party after seeing his play The Birthday Party. She was 42; he was 44. Before leaving, she went over to congratulate him. "He looked at me with those amazing, extremely bright black eyes. 'Must you go?' he said."

He gave her a lift home and she served him champagne. "He stayed until 6am with extraordinary recklessness, but of course the real recklessness was mine." They never looked back.

It wasn't all wine and roses, however. Among Pinter's mementos after he died, Fraser found a message she had jotted on a place card at a table where he was having one of his rants. It read: "Darling - you are right. So SHUT UP."