Matthew Bell: The <i>IoS</i> diary

As an enthusiastic Twitterer she gets full marks for being "on trend". So it pains me to reveal Sarah Brown has gone two steps back by joining Facebook, which some readers may recall was once all the rage. The Prime Minister's wife managed to resist the temptation to join when it was fashionable, but now the circus has moved on she has quietly signed up. Although so far she only has 24 friends, they are a carefully selected group, numbering Piers Morgan, Martha Lane Fox, Emma Freud, Claudia Winkleman and the Times columnist Janice Turner. But perhaps the most intriguing friend is Jo Dipple, the former senior adviser to Gordon Brown who caused him some embarrassment by quitting last autumn. Who will befriend her next – Damian McBride?

When Peter Hain once suggested Labour might raise the top level tax rate, Blair and Brown were furious and publicly rebuked him. It's said that Gordon even telephoned various newspaper editors to denounce Peter Hain as a "moron". It was an interesting choice of words, one famously used in a song by Jilted John, "Gordon is a moron". Alas this refrain is often used of the Prime Minister, appropriately enough now that he has raised the higher tax rate to 50p.

Watch out Miss California – Alan Duncan wants to kill you. The shadow Leader of the House of Commons made the astonishing threat in an unguarded moment during the recording of Have I Got News For You, which was broadcast on Friday. In a sequence about Miss California, who believes same sex marriages are wrong, Alan Duncan appeared to have a sense of humour failure, saying "If you read that Miss California had been murdered you'll know it was me, won't you?" The remark drew a sharp intake of breath from the audience, but Alan Duncan now says it was all just a joke. "I haven't seen it yet so I can't really comment, but of course it was in jest – it is a comedy show after all," he told me, "I'm sure she's very beautiful and that if we were to meet we would love each other. I have no plans to kill her. I'll send her a box of chocolates – unpoisoned."

Intriguing to hear Ken Boston, the man responsible for the SATs fiasco, accuse Ed Balls and Jim Knight of "sexing up" evidence against him. The former exams chief says he was wrongly portrayed by the two ministers in evidence they gave to an official inquiry. Boston says they had been plotting to oust him since March, but as it happens he didn't resign until December, when a Sunday newspaper revealed he had lavish perks written into his contract, including membership of a yacht club. It remains unclear how the paper got its story, but in the light of the McBride scandal perhaps it's not so hard to imagine.

The rivalry between David Cameron and Boris Johnson intensifies, as Francis Elliott and my colleague James Hanning reveal in their revised biography of Cameron. Indeed communications between the pair are so strained that an insider admits they only speak "from time to time". When the Evening Standard claimed Boris may only run for one term as mayor, Cameron did not ring Boris, but left it to his right-hand man Andy Coulson, who spoke to Boris's senior aide Guto Harri, a former BBC journalist. Asked by a journalist about Boris's plans he said "Who knows? Do you know where you'll be in five years time?"

She stars in the new Terminator film out next month and has a career many Hollywood starlets can only dream of. But Helena Bonham Carter has little interest in the usual pursuits of A-list actresses. Last week she popped in for the opening night of an exhibition of portraits by society photographer Cecil Beaton at the Chris Beetles Gallery in central London. The gamine actress sensibly arrived early to snap up a portrait of her great grandmother Margot Asquith, priced at £3,500. Red dots were appearing fast, with pictures of Pablo Picasso, Lucian Freud and Audrey Hepburn selling particularly well.

m.bell@independent.co.uk