Oops, the media circus has done it again ...

Britney Spears is learning that when the press turn on you, you've had it.

At the London premiere of her film Crossroads last week, the singer Britney Spears swanned up to the red rope, surrounded by bouncers the size of refrigerators, refusing en passant to sign her autograph for the waiting fans. Instantly, the papers downgraded her from virgin goddess to vicious megabitch. Meanwhile, in court, Naomi Campbell won her spat with The Mirror but came out looking broken, her reputation as a vain monster utterly confirmed. Again, it has been proven – like the stock market, celebrity reputations can go down as well as up.

Take Kate Winslet. Only a year or so ago, she was a paragon of plain British niceness ("our Kate!" the tabloids cooed, turning her into a kind of millennial Vera Lynn) until she chucked her husband Jim Threapleton, moved on to alpha romeo Sam Mendes, lost weight and started kicking back in Babylon, Los Angeles. Then she became our village witch, ready to be ducked in the poisonous pond of public opprobrium.

Anthea Turner was a successful Stepford celebrity on the sofa-and-quiz-show circuit until she began a relationship with a married businessman, Grant Bovey, enticed him away from his wife and three daughters and lured him like a siren into the media circus. It turned Turner from a nice-but-bland TV blonde into a bunny-boiling baggage – and the public rewarded her by buying just 451 copies of her autobiography, Fools Rush In, in its crucial first week. And where (as they say) is she now? (Before writing the "sexist" letter, remember that it works for men as well: Will Carling was monstered for leaving his girlfriend and child.)

Much of the joy that the public takes in such tales is driven by our dear old friends, envy and schadenfreude. These feelings are particularly acute when a celebrity has become too big for his or her boots, but in general we like to see successful people fail – emotionally, financially, physically – like some latter-day Icarus, deservingly burning their wings on the spotlight. It's a Brit thing: we like people to be taken down a peg or two, to be deflated and even destroyed.

No matter that Tom Cruise diligently signed autographs alongside his new girlfriend, Penelope Cruz, at a film premiere last year. His split from Nicole Kidman meant the damage was done, and if she was going to come out smelling of roses – in the public's eyes, at least – then Tom was only going to jeopardise his public standing. Tom and Nicole were the golden couple: how dare he shatter our illusions?

Max Clifford, who has laundered many reputations in his time, thinks that the celebrity downfall is often avoidable. "We love to build people up then knock them down in this country," he says. "And of course, a lot of their problems are due to personal circumstances.

"But it isn't just that. Often it's bad advice from the people around the star – the PRs, the security – who will justify their existence by making a mountain out a molehill, or create problems with no grounds whatsoever." If Spears had been told to take a bit of time to sign autographs, her reputation wouldn't necessarily have been damaged.

Spears's case highlights another factor: that there is a translation problem between the US and the UK. "Stars have enormous egos and their people pander to them over there," says Clifford. "If the star wants it to be Tuesday, even though it's Thursday, they'll tell them that. The British people demand humility from stars, which is quite different. David Copperfield [at one time a Clifford client] became a legend in his own mind, and at that point the British didn't take to him." True: to us he was a bizarre haircut and an orange tan who somehow had managed to end up with Claudia Schiffer.

When difficult stars (such as Naomi Campbell) are involved, the public satisfaction in their descent is palpable. Mariah Carey, notorious for being the kind of star who demands asses' milk in her backstage rider, suffered from "exhaustion" and although she received a vast pay-off from EMI, many were delighted at this come-uppance. Indeed, sometimes a kind of altitude sickness can prevail, causing the celebrity to become self-destructive. Whitney Houston, for instance, became involved in a drugs case that was entirely avoidable and which, in US terms, destroyed her credibility.

Some celebrities fade away, others plummet out of public favour, others return to delight us once more – as if swimming on the whimsical tide of public opinion. Here, a strange consensus often reigns – it is near-compulsory to deride Minnie Driver, for instance, and Stephen Fry is periodically given a hard time. As for the likes of Jordan and Lady Victoria Hervey: they are figures from the world of pantomime, bottom-shelf public commodities to be used and discarded at will.

OK, so how to maintain your stature? Stability is admired, particularly in marriages – if only because it comforts us that the celebrity has less sex than we do. The Beckhams have maintained their public standing, and Paul McCartney has survived well, as if trying to disprove Montaigne's dictum that "fame and tranquillity can never be bedfellows". Really, all tall poppies need is self-knowledge, self-control and good management.

Will the public respond by staying away from Britney Spears's new film? Well, like the Roman emperor's thumbs down, not buying the work is the most damning statement. As for Spears, she should take advice from Courtney Love, who was shown on a TV programme last year having a tantrum. Why? Because no one had asked for her autograph.