When Gordon Brown finally gets to lay out his pencils and pocket calculator on the desk at No 10, there could be an unexpected welcome gift waiting for him. Tony Blair apparently wants to install his own loyal chief of staff as the new ambassador to Washington.

Jonathan Powell has been the prime minister’s closest aide ever since Labour came to power in 1997. But that’s not the only reason he is disliked by Brown supporters. Two years ago Powell got chatting with Tory MP Boris Johnson as the pair cycled down Pall Mall. “Gordon Brown is like the guy who thinks he’s going to be king but never gets it,” Powell is alleged by Johnson to have remarked. “It’s like a Shakespearian tragedy.”

The timing would be just right for Blair to get his man in the job before stepping down. Our man in Washington, Sir David Manning, finishes his four-year posting next year. The safe-pair-of-hands candidate would be Sir Nigel Sheinwald, who took Manning’s previous job as Blair’s chief foreign policy adviser. If Blair doesn’t find a niche for Powell, his thoughts might just turn to writing his memoirs. Which might not be that fun for Gordon either.

Hideously lucky – Cameron puts his faith in green tie

At last we can reveal the secret of David Cameron’s success — it’s all down to his lucky tie. The Conservative leader’s modern, compassionate open-necked shirt look is well known, but when he got the job he was wearing a bright green tie. So if a big occasion calls for a tie, that’s the one.

“It’s hideous,” complains an aide, “but he was wearing it when he was elected so he’s convinced it’s lucky.” And so very Blairite.

The prime minister has a special striped tie that he wears in moments of crisis, it was revealed last week. Cameron is just making sure he can’t be outflanked in the vital matter of neckwear policy.

• Good news for Cameron, though. The BBC is planning a special programme for Christmas that portrays the first days of a new Conservative government.

  The slightly less good news is that the programme is a special edition of The Thick of It, which has mercilessly ridiculed the spin and incompetence of ministers and their advisers.

  Is Boris a speed freak? You do the maths

  Only a crouton spends more time in the soup than Boris Johnson. He was criticised last week for putting his two young sons in the front seat of a Lamborghini. “If anyone says I was speeding,” he says, “I want to see the evidence.” Yet in GQ magazine he nearly incriminates himself. Road-testing a Ferrari, Boris invites readers to calculate his speed: “Take the number of virgins that suicide bombers expect to find in paradise, double it, then subtract the percentage of 18 to 30-year-olds in higher education in 1964.”

  The 72 virgins double to 144. Which means Boris needs a higher education figure of 74% to get down to the 70mph limit. The current target is 50% by 2010. No wonder Boris adds hastily: “This review is essentially a work of fiction.”

• The job comes with £70,000 a year, light duties, a mansion and a butler when required. So you’d think clerics would be queueing up to become Dean of Westminster. Yet after nearly a year the post is unfilled. The latest candidate to be considered is Robin Griffith-Jones, who at least has seen a dramatic surge of interest in his church in recent years. He is Master of the Temple in London, as featured in The Da Vinci Code.

  “We get about 50 visitors a week,” he once explained, “all asking whether we have read the book. The verger thinks they mean the Bible.”