Cheeky chic

Bay Garnett, the queen of thrift, is meeting me in a crowded coffee bar near her Notting Hill home. I'm worried about recognising her in the seething throng.

'Oh, I'll be the one looking a mess, that's how you'll know,' she says. And, of course, when she swings through the door, I spot her immediately. Not because she looks a mess, but because she stands out from the common herd like a panther at a cat show.

Statuesque, with Pre-Raphaelite curls and the face of a Madonna, she's wearing a brown suede skirt, a tie-dye effect jumper cinched in with an enormous old leather belt and a sage-coloured shawl. A pair of tiny gold handcuffs dangles from one ear.

Bay is one of fashion's best-kept secrets. Co-founder of the New York edition of Cheap Date, the anti-fashion magazine that extols the virtues of rummaging through charity shops, she has presided over the rediscovery of 'vintage' by all of Hollywood's big-name actresses.

She's a muse for the British designer Matthew Williamson (who, the following day, will be with her as she puts together ensembles for this month's New York show).

At Christmas, Topshop sold a much-sought-after line of dresses 'inspired by Bay Garnett', found by her in thrift shops and customised by the store. She's best friends with supermodels Sophie Dahl, Erin O'Connor, Jade Parfitt and Karen Elson, and hobnobs with the industry's most credible and sought-after young photographers.

She's also a contributing editor to British Vogue, for whom she recently styled Kate Moss wearing Anita Pallenberg's old clothes.

What makes her all the more remarkable is that she is only 30 years old and has no fashion training. What she does have is a very good eye, nurtured by years of trawling for bargains in rural charity shops.

Deconstruct today's outfit, for instance: the wide leather belt (Eighties Ralph Lauren), the jumper (Trussardi) - 'I love it, it looks like it's been picked up from the bottom of a campfire' - and the jewellery (a gold wishbone and a tiger's claw set in silver) all came from charity shops.

Her ancient Chanel purse was given to her by Karen Elson and the shawl is a boyfriend's castoff. Only the skirt, in fact, is new. So while she may look a million dollars, the total cost of her outfit probably doesn't exceed £100.

It's a point she's made forcefully in a witty campaign that runs in the current issue of Cheap Date. She has dressed supermodels such as Alek Wek and Trish Goff in charity-shop castoffs, then had them photographed in the style of well-known advertising campaigns: Burberry, Calvin Klein, Cartier, Prada.

In the Cartier 'Castoff' advert, Goff is wearing Bay's own tigerclaw necklace; the Calvin Klein 'Cancer Care' model is wearing her Seventies thrift-shop Keds.

The images are glossy and covetable, and the point is forcefully made: why buy expensive designer clothes when, with a little thought, you can achieve a similar effect at a jumble sale? The juggling act that Bay manages to pull off, however, is that the fashion industry loves her. She has become fashion's anti-fashion mascot, proof that there is a sense of humour in its po-faced, profit-driven world.

The latest issue of Cheap Date, for instance, is sponsored by Jigsaw, although there isn't an ad for their clothes in sight.

We aren't the enemy,' Bay explains. 'The images aren't piss-takes - they are a tribute to the power and beauty of the images of the fashion houses. I'm trying to get a bit of fun back into fashion. We're saying you can look great for a few pounds, you can be individually stylish.'

Naturally, as befits the thrifting ethos, the campaigns have cost the magazine nothing, rather than the £50,000 each they are 'worth'.

The models and the photographers Craig McDean and Glen Luchford gave their services free, as did Pascal Dangin, who is the magazine's creative director and, in his day job, a retoucher whom Bay calls 'the most powerful man in fashion'.

He works for Annie Liebowitz and Steven Meisel, giving their pictures the gloss we expect. 'When we're doing it, it's really fun,' she explains.

What about the cost of the studio space and the lighting? 'We snuck in at the end of a shoot I was styling, with the stuff all ready,' she says, 'and shot it in about five minutes after the client left so as not to run into time we hadn't paid for.'

She giggles. 'It's really guerrilla.'

Bay, it seems, is used to getting things done efficiently. Polite and straightforward, she expects no less from those she deals with. A certain world-famous model, who is as well-known for her lateness as for her beauty, received short shrift.

'She kept me waiting seven hours, so I decided to leave,' she says. 'Nobody has the right to treat anybody like that; we're all humans, after all.'

Her down-to-earth approach is a result of her rural upbringing. She is the daughter of writer Polly Devlin and Adrian Garnett, an engineer and inventor, and sister to Daisy, 31, who works at Vogue, and Rose, 33, a full-time mother.

She started her thrifting career visiting carboot sales and flea markets with her mother. 'Someone told me recently that she'd always known I would work in fashion because of the way I dressed at school,' she says.

She studied art history and modern history at Exeter University. She then worked at the Peggy Guggenheim Collection in Venice, before being offered a job in New York as a fashion stylists' agent in 1999. 'I was hopeless,' she says.

'I kept losing everything, but they liked me because I was cheerful.' She shared a flat with Sophie Dahl and started dating Paul Sevigny, the brother of her friend and fellow thrifter, the film star Chloë.

Then she was invited by Kira Joliffe, founder of Cheap Date in London, to help start up a New York edition. Stylists she represented began asking to borrow her clothes for their shoots.

Examining their work, she says she thought, 'I could do this standing on my head.' And when, two years ago, she met Matthew Williamson, she had no difficulty persuading him the same thing. Cheap Date has a small circulation but is disproportionately influential. Liv Tyler is a fan and so Bay is invited everywhere.

She is now back living alone in West London, although she still prefers the charity shops on New York's Upper East Side.

Her personal holy grail is Seventies Yves Saint Laurent. 'The man was a genius,' she says, proud owner of a Cossack coat ('It cost $200, but it's worth a fortune').

And her future plans? 'I'm thinking more and more about designing myself. I don't know if I'm together enough, but it would be really fun if someone would throw money at me, set me up with a pattern-cutter and ask me to come up with a collection.' Watch this space.

Vintage advice: Bay's thrifting tips

Rural charity shops are always a good bet. In London, head for World's End.

Don't take a day out to thrift; just pop in every time you pass a charity shop. It might be a desert one week, a goldmine the next.

Go in with an idea of what you're looking for.

Take clothes out of context: they may look horrible in the shop, but imagine them teamed with what you've got at home.

Don't buy anything irretrievably stained.

Don't worry about making mistakes - at least they aren't expensive ones.