Forget your vertiginous Manolos and put away your fancy Jimmy Choos. The footwear of the moment is a cross between a pair of wellies and granny’s sheepskin-lined clodhoppers. They’re not sophisticated and they’re not sexy, but right now, Ugg boots are considered very, very cool. The ultimate celebrity taste-makers — Kate Moss, Madonna, Sarah Jessica Parker — are wearing them. And everyone who is anyone owns a pair. Everyone, that is, who was ahead of the game. Go out now and try to buy a pair of Ugg Classics (about £140), and you will be coming home disappointed. The fluffy boots with the toy-town round toes and the seriously unflattering straight-up-and-down leg shape are a sellout — everywhere.

“We’ve had to re-order them three times,” says Yeda Yun, buyer at Browns Focus in London. “It’s phenomenal. Demand has hit the roof. We began in November selling black and sand ones, then moved on to every colour. People just want more.” It’s the same across the country — and even across the Atlantic. American retailers booked 20,000 pairs of the new baby-pink and baby-blue boots before they had even seen a sample.

They are now sold out until May. Retailers just can’t keep up with demand, and, as a result of Ugg’s new-found popularity, there is a global shortage (production is gearing up in China as well as Australia and New Zealand). The company’s share price, needless to say, has gone through the roof, increasing by 700% last year.

So, why the clamour for this Ugg-ly boot? How has this trend come about? You could put it down to comfort. Ugg boots were created by an Australian surfer intent on keeping his feet warm while on shore. Designed to be worn barefoot, the sheepskin cleverly keeps feet comfy in temperatures as low as -30F and as high as 80F. And, I have it on good authority that wearing a pair is like walking on cotton wool.

If you speak to a cool-hunter, they might tell you the trend for these hefty boots is a natural progression: a step on from shapeless Maharishi pants and sexless parkas, and a backlash against worked-up sex appeal. Why have these all been such a favourite with the beautiful people? They operate with the subtext: “I’m so beautiful/thin/stylish, I can make even this look great.”

In fact, these are both side issues. The reason the boots are such a must-have is simple. Ugg, or rather its parent company, the California-based footwear giant Deckers Outdoor Corporation, has made it its mission to court celebrities — and, as we know, stars shift product. Working on this tried-and-tested formula, Uggs were sent to stars on film sets and music videos, a cosy perk while on location. Lo and behold, the credits in Heat and Hello! started to flood in. Not worn only for off-duty fashion moments, the boots made it into films such as America’s Sweethearts and American Pie 2, and appeared on television in Friends, Will & Grace, Everybody Loves Raymond and Dawson’s Creek. Sarah Jessica Parker even had a ruby-red pair made for the final series of Sex and the City. In America, Uggs have percolated down the style chain. Oprah Winfrey claims they are one of her “favourite things”, and Pamela Anderson, a vegetarian, who likes to wear hers with a bikini, is rumoured to be setting up her own company to make an animal-product-free version. The boots look set to go mainstream over here, too: 500 pairs were imported to Britain last year; more than 150,000 pairs will hit Europe later this year.

But fashion is famous for its short attention span. How can Deckers sustain this growth? A shortage of supply and a range of limited-edition new colours will maximise the boots’ fashion status in the short term; long-term, however, the canny company has ensured that boots are just the tip of the iceberg. Ugg makes shoes, slippers, clogs and outerwear from the same Australian sheepskin. (Its shearling Lola jacket has already made its way into the wardrobes of SJP and Renée Zellweger.) There are also plans for a sideline in handbags that ooze fleece from the seams, and an ultra-shaggy collection that will work with the Fluff range of yeti boots, complete with a preposterously furry Fluff muff. With these, Ugg has all the components to become a big lifestyle brand.

Meanwhile, although British supplies of the boots are exhausted, demand continues. “People who missed out this time round will go for them next winter,” says Yun. “Of course, there will be a lot of copies around by then, and they won’t be so cutting-edge, but they will still be going strong. They appeal to the same customer who wears Maharishi pants and Juicy Couture tracksuits.” Probably not the beautiful people (they will have moved on), but the rest of us, who have all summer to dream up the impossible: a flattering Ugg-booted outfit.

Ugg; 0800 072 5164, www.uggaustralia.com

OTHER FLASH FADS

They launched leagues of waiting lists and a zillion rip-offs, and these style curiosities maintain a loyal following even though the fashionistas have moved on.

Bowling bags
Bi- or tri-coloured, Prada’s bag was a triumph of paparazzi power over aesthetics. Ultra-groomed Elle Macpherson carried one, and suddenly what once looked nerdy became chic.

Snopants
Low of crotch and baggy on the hip, Maharishi’s trousers are not the most flattering, but they found a large following among expectant mothers.

Velour tracksuits
Juicy Couture’s take on trailer trash was a hit with J.Lo and Catherine Zeta-Jones. And the plush fabric still finds favour with frequent flyers.

Parkas
When Kate Moss was photographed wearing one over skimpy evening wear, the parka suddenly became newly cool. It may be off the fashion radar now, but the cosy winter warmer still sells.

Combat jackets
Marc Jacobs’s catwalk original, with big buttons and multipockets, is still being plugged on the high street.

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