From Liam Byrne, the new Minister for the Cabinet Office, comes a leaked memo that strikingly illustrates the strange madness that often comes from a modicum of power. Mr Byrne likes things just so, and he has laid out those things very precisely in a document for his civil servants entitled Working with Liam Byrne.

For example: “Coffee/Lunch. I'm addicted to coffee. I like a cappuccino when I come in, an espresso at 3pm and soup at 12.30-1pm.” The Diva of Downing Street continues: “The room should be cleared before I arrive in the morning. I like the papers set out in the office before I get in. The white boards should be cleared. If I see things that are not of acceptable quality, I will blame you.”

Briefing notes, he decrees, must be on a single page, and the type must be large (16 point). “Never,” he insists, “put anything to me unless you can explain it in 60 seconds... It is your job to keep me to time.” This goes on for 11 pages. Moreover, it was written in 2006, when he was still a junior Home Office minister.

Mr Byrne is exhibiting all the classic symptoms of Mariah Careyensis, an ailment that afflicts ageing film stars, highly strung supermodels, tottering dictators, big fish in small tanks, otherwise entirely sensible politicians who feel the need to exert their authority and, in this case, ministers who used to be management consultants. Symptoms include referring to oneself in the third person, framing personal foibles as unshakeable rules, delusions of grandeur, holidaying in Corfu with Russian billionaires and requiring underlings to peel oranges for you.

Unless Mr Byrne is treated quickly, he may start insisting on a new loo seat at every tour venue (Madonna), demanding that the green leaves be cut off the red and white roses in his dressing room (Elton John), or banning “distinct smells in the vicinity of the artist” (the late Luciano Pavarotti, a man of outsize olfactory sensibilities).

Powerful people develop very specific needs: Beyoncé Knowles, it is said, demands extra-spicy chicken wings and a dressing room at exactly 25C; Prince Charles requires a footman to squeeze his toothpaste; Mariah Carey doesn't do stairs and the new Minister for the Cabinet Office must have his soup by 1pm.

Mr Byrne would no doubt defend his detailed instructions on the grounds of efficiency, but in truth his memo is the latest evidence of a rule-obsessed regime, fixated with managing the process of politics. Just as the pop star becomes more demanding and truculent as his powers wane, so political organisms tend to become more fastidious and controlling with age.

The word diva, coined in the 19th century, comes from the Italian divina, meaning divine, an accurate root for the sense of godly entitlement that comes with too much attention, and too much power.

So far from reflecting confidence, extreme diva behaviour is more often evidence of superstition, and a peculiar celebrity paranoia. The prima donna who needs to be kept at a specific temperature and protected from smells is secretly worried that if anything disturbs her equilibrium, she will be unable to perform.

Similarly, self-conscious and anxious politicians seek to control the environment, often in eccentric ways. Cardinal Wolsey insisted on carrying oranges studded with cloves wherever he went, in case he caught a whiff of the common herd.

In Working with Liam Byrne, the minister declares “we need to produce a grid” on which to hang the news of the week. “Moving something from a grid slot is a very, very big deal,” he says. Perhaps the most chilling element is his order that advisers tell him “not what you think I should know, but what you expect I will get asked” - an almost perfect distillation of new Labour's approach to government, in which what you know or believe matters far less than giving the right answer.

A grid-like approach to politics is almost certain to produce gridlock. Some things cannot be explained in 60 seconds. A politician should be able to absorb information in whatever form it comes, just as the confident artist can perform regardless of circumstances. The spiciness of the chicken and the rose foliage should be as irrelevant as the point-size on a briefing memo.

One of the more encouraging, aspects of Barack Obama's election campaign was his complete lack of prima donna fussiness. He is reputed to be sublimely indifferent to his surroundings, creature comforts and the size of the hotel bathroom. Where George W. Bush insisted on travelling with his own pillow and liked to be tucked up by ten, Obama barely noticed where he was sleeping and seemed able to drop off, like Winston Churchill, almost at will.

The campaign trail is such an uncomfortable place that candidates swiftly become finicky about how they travel, whom they see and what they eat. Night after night Mr Obama dined on salmon, rice and broccoli, not because he insisted on it, but because it was simplest to order.

Young regimes and new performers do not care about the cleanliness of the floor, the size of the bouquet or the shape of the briefing note. Those preoccupations come only towards the end of a career and a government, when the minutiae and trimmings matter more than the performance itself.

It is hard to imagine America's new president handing out Working with Barack Obama to aides, let alone establishing a timed soup schedule or having his toothpaste squeezed by an underling. Then again, he had barely tasted power yet: not every celebrity succumbs to Mariah Careyensis, but few are entirely immune.

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