Tanya Gold: Lady Antonia's latest epic – 'I Love Me'

The historian's grip on reality is weaker at home

Harold Pinter's reputation is in danger. Who would dare put it in jeopardy? Lady Antonia Fraser, his widow. When I first picked up her memoir, Must You Go? – these were his words to her on the night they met – I thought it was a joke. Someone should have stopped her, or suggested she call it I Love Me instead.

The critics call it insightful. It is, in the sense that, quite unconsciously, the protagonists emerge as a pair of total idiots. Lady Antonia cannot stop complimenting herself either in the first person, or through quotes from friends, which she has copied down. Bereft of Pinter's worship – he died in 2008 – she writes a love letter to herself. "He really seems mad with love"; "It's very serious for Harold"; "He's much enraptured"; "'You looked so beautiful'." This is narcissism cubed.

And always the mantra of the playwright to his love: "I am the luckiest man in the world." Anyone else writing this guff would have been beaten to death in the pages of the TLS. When asked how she copes with Harold mentioning former girlfriends, she says: "It's the memorable path that led him to wonderful me!"

If the vanity is hilarious, so is the prose. "I floated... as in a dream towards him"; "I long to bathe his fevered brow"; "All I can do is shelter you under the wide umbrella of my love"; "He had a lovely dream that we were both in California... and I looked very beautiful".

It would be bearable if she weren't so snobbish, complaining about the hated press all the time while clearly adoring the attention, and making snide comments about Harold's PhD acolytes. You would have thought that the daughter of the Earl of Longford, on marrying the left-wing Pinter, might have dropped her title down a manhole. Instead, she complains that Jilly Cooper is seated next to Anthony Powell at a lunch: "Being an earl's daughter, I had to be on the right."

But the snobbery isn't as bad as the cruelty. Pinter left the actress Vivien Merchant for Fraser, and Merchant later died of alcoholism. Couldn't Lady Antonia – rich, successful and loved – spare some pity? No. She seems angry that Merchant didn't just obediently melt away, as her own husband, Hugh, was happy to do.

Her pronouncements on Merchant have understated venom. Fury would have been less ugly. "Vivien believed to be in a caravan in Scotland with her carpenter admirer"; "Like many... who seek vengeance, she herself ended up by being the final sufferer". Merchant's refusal to sign divorce papers was "a final flick of the serpent's tail".

When Merchant finally dies in 1983, at the age of 53, Fraser doesn't even mention it. This can hardly be tact, not in a diary stuffed with observations about dresses and swooning over Harold in public places, as the couple enact Duel in the Sun in South Kensington. The first entry after Merchant's death reads: "World Premiere of Other Places at the NT". There is no mourning for Pinter's companion of 20 years, but she does lament the loss of a tree in her garden, gnawed by a squirrel. I applaud that squirrel.

Even Joan Bakewell, whom Fraser is supposed to like, gets it in the neck for her presumption. She was Pinter's lover for many years, and she inspired his play Betrayal. This hurts Antonia, who needs to be centre of everyone's obsession. When Bakewell writes her own memoir, The Heart of the Matter, Antonia trashes her in the usual, polite passive-aggressive schoolgirl style.

"Friends and family... think that Joan has made rather a meal of the whole thing. I know that Harold had a more intimate relationship at the same time, with a woman he called Cleopatra." Yeah, Joanie – he never loved you! He loved ME! It's all about ME!

And how does Harold Pinter emerge from the pink-princess prose of Must You Go? Not well. Because the evidence for future biographers is all here. He loved this.