Rebecca Tyrrel: For the love of Audrey

A secret bidder paid half a million for a dress the star wore, an example of the enduring allure of a movie icon

There was a rumour doing the rounds of the tabloid gossip columns this week that it was Victoria Beckham who had bought the Audrey Hepburn, Breakfast at Tiffany's black dress at auction. Certainly Posh could have easily afforded the record-breaking price of £467,200 - pretty much what she and Becks might spend in one afternoon's saunter down Fifth Avenue, Manhattan, which is where the Givenchy dress's big moment was filmed in 1961. The Daily Telegraph, however, says Mrs Beckham couldn't have been the anonymous telephone bidder, despite being a die-hard fan of Audrey Hepburn, because she didn't even know about the sale.

So that solves that puzzle. But how would a rumour like this start? Could it be that the gossip columnists could think of no one else rich enough or thin enough, no one else who could possibly wear such an iconic yet minuscule slip of a size six thing? (Audrey Hepburn was every bit as skeletal as Posh owing not to an unhealthy preoccupation with weight, upon which we must frown, but to entirely unblameworthy wartime malnutrition in childhood.)

More likely is that the rumour was started when the opportunity to pitch the two women against each other became too much to resist. They even threw the larger-sized (but certainly not fat) Coleen McLoughlin into the mix at one stage, but the Beckham/Hepburn juxtaposition was quite exciting enough and the McLoughlin camp, though clearly flattered, pointed out that Coleen couldn't possibly have been the buyer because she was working that day and would not have had time to hang around on the end of a phone to Christie's - not even to purchase one of the most important dresses worn in any film ever.

So we were left to mentally toss around the Victoria rumour - on the one hand we were given the ever-lasting, serene image of the late Hepburn (she died in 1993) as wistful, woeful Holly Golightly, window shopping and daydreaming in the early hours of the morning along Fifth Avenue wearing an impossibly elegant column of black silk crêpe, and on the other the chav version. Victoria is the not quite beautiful, failed pop-star teetering out of the Ivy with a footballer on one arm, a Giambattista Valli handbag and a tetchy pout for the paparazzi on her face.

But poor Posh. She never asked for this, she's got quite enough dresses already, and the comparison is cruel. No one in the world will ever be as exquisite as Audrey Hepburn, and no single image of Audrey is more memorable or compelling than the one created during the opening moments of the film version of Truman Capote's book. That Givenchy dress was only one of many winning components in the scene, in which even Holly Golightly's takeaway breakfast - her early morning croissant and coffee - had charisma along with the unaffordable diamonds in Tiffany's windows, the smooth lines of the beige Manhattan buildings, and Audrey herself, her long neck, her sophisticated chignon, the baby doe eyes, faultless nose and perfectly shaped, entirely untetchy lips. All that was required of the director, Blake Edwards, was that he just leave her be, let her eat from the bag, sip from the cup and look dreamily into those windows. All Audrey had to do was be Audrey.

No further instructions were necessary - and a marvellous film moment was made.

Forty-five years on at Christie's auction house it didn't really matter who was making the successful bid for the dress, famous footballer's wife or unknown philanthropist. Only good can come of the sale of this single garment (although there are further rumours which say that it isn't in fact a single garment at all, it is one of three made for the film; indeed, rather embarrassingly, it might not even be the one in the final take).

Whatever, and who cares? The money raised will go to the City of Joy charity in Calcutta. It will help children who are living with disease and poverty - just as Audrey Hepburn, sleeves rolled up, out in the villages, already suffering from the cancer that killed her, helped in her role as Unicef ambassador. You see, in our eyes, Audrey can do no wrong, only good. And posthumously she still does good. The dress - which set a world record for the price tag attached to a film costume - was worth every penny.

In 1999 another dress, just as iconic though not a film costume, was sold for £583,000. This time it was a Jean Louis-designed sheer flesh-coloured nylon slip, encrusted with 2,500 rhinestones. What set this dazzler apart was its history: the slip once belonged to Marilyn Monroe, and she wore it on 19 May 1962 at Madison Square Garden in New York, the occasion being John F Kennedy's birthday.

Adlai Stevenson, a Democrat and failed presidential contender, described this piece of flimsy almost nothing as "skin and beads" - and indeed it was so tight that Marilyn had to be sewn into it and cut out again in the early hours. Why did it fetch such a high price? For a start there was the rumoured relationship between Monroe and Kennedy, and if Marilyn was trying to keep things a secret, she wasn't trying hard enough as she couldn't have looked sexier as she sang him Happy Birthday. Tragically and also significantly, this was her last major performance. So this was every bit an iconic moment - an icon performing for an icon and the only thing left is the iconic dress she wore.

Geri Halliwell wore a lookalike version when she serenaded Prince Charles at Highgrove on his 50th birthday. But her version was not in the same class at all. But then it's a strange class to qualify for. Take, for instance, the even more famous Marilyn Monroe dress: the white halter neck with pleated skirt that behaved so impeccably when placed over a hot air vent for the shooting of The Seven Year Itch in 1955. This was dumb, ditsy Marilyn on display, sexy in a different way, a different, lesser kind of icon - less tragic, less disturbing and not worth half a million pounds. It is a dress, however, that has generated far more money over the years than the JFK number because it has been copied again and again, sold in cheap fabrics for low prices on internet sites and in costume shops and worn to fancy dress parties and hen nights. It's not classy and, unlike Audrey's dress, it always looked like costume, not fashion, even on Marilyn. It didn't create a fashion, it didn't change the way the public dressed. But then, she wasn't Audrey.