Erin O’Connor is one hour and 15 minutes late. So far so supermodel. She arrives eventually at the office of ICM Models in Covent Garden clutching a Prada handbag, and is immediately handed a Chanel shoebox.

Now most supermodels wouldn’t get out of bed for anything less than Imelda Marcos’s entire collection, but O’Connor is different. “Oh, how kind of them!” she says with genuine gratitude, rolling her eyes in delight.

She is similarly enthusiastic about her modest new car, parked outside on the cobbled streets. (Well, it’s not hers exactly, it is a gift from Fiat, loaned to her in return for the modelling work she’s done for the company.) “It’s really very nice, isn’t it!” she exclaims, casting her eye over the bright blue hatchback. “There’s a bit of bird poo on the back there though. This one isn’t mine,” she adds, explaining that she’s still waiting to have hers delivered.

O’Connor, 28, is one of the highest paid models in the world, has worked for everyone from Valentino to Dior and is now, alongside Twiggy, one of the faces of Marks & Spencer’s latest ad campaign — but she has only just learnt to drive. The Grande Punto, when she finally fits its delivery into her busy schedule, will be her first car.

“I haven’t really got a clue about cars. It’s an absolute luxury being driven from gig to gig but at some points you do feel rather hopeless. I started driving lessons two years ago because I wanted to be able to carry myself off to places.”

The Fiat is a down to earth choice for a famously grounded kind of supermodel — “the nice face of fashion” — although she admits her dream car would be a not so down to earth Maserati. True to reputation she is grovellingly apologetic for her tardiness, saying: “It’s like Challenge Anneka for me at the moment!”

While waiting for her arrival I’ve been working my way down the bowl of Cadbury’s Roses in the ICM reception, and O’Connor joins me in a chocolate caramel. We have a “five-minute window” for pictures — a far cry from couture. Just time for O’Connor to whack on some lip gloss and pinch her cheeks — “I want to at least look healthy!”

Seconds later, still trying to retrieve stray bits of toffee from her back teeth, O’Connor — all gangly 6ft 1in of her — is sprawled (well almost) on the Fiat’s bonnet. “I’ve never been asked to do ‘those’ kinds of shoots,” she jokes.

Then she turns on the pout and works the statuesque, angular good looks that have won her the adoration of top designers, and which — thanks to the contract with M&S — have now blasted her regal profile onto 20ft-high billboards across the country. “It is such a gloriously big deal,” she says, “because I’d always thought that I’d never be a poster girl. Now I get the odd cabbie shouting, ‘You’re the M&S girl aren’t ya?’ It’s nice.”

Always much more than a striking face, O’Connor was recently made vice-chairwoman of the British Fashion Council, the organisation behind London Fashion Week, which kicks off next Sunday and is leading the drive to bring top designers back to the capital’s catwalks.

Her skinny frame has meant that she has also found herself at the centre of the latest debate about “size zero” (UK size four) models, following London’s decision not to follow Milan’s ban on models with a BMI (body mass index) of less than 18. “I think it’s important to have the debate to a degree, but sensibly and without judgment,” she says. “I’d like us all to think a little deeper. Eating disorders are terrible things, whether you’re underweight or overweight for that matter.”

For the record, O’Connor claims she is size 10-12. “But it’s a terrible thing that I have to, in a sense, justify my frame.”

Away from the extravagance of the catwalk, she prefers to keep life simple. Following a brief sojourn in the gossip pages thanks to a relationship with the TV presenter Jamie Theakston, she is now settled in southeast London with her boyfriend of two years, John Paris Kent, or JP, a television producer. “All he sees of my work is when I come back home and I’m smudging my make-up off,” she says. “That’s the way I prefer it.”

They moved into their refurbished Georgian town house just before Christmas and have developed a mutual love of the great outdoors. “We’re big camping fans, if you can believe it,” says O’Connor. “We plan to shove the tent into the back of the car and head down to the south of France. I think after the whole controlled environment in which high fashion takes place it’s just a real joy to do something more basic.”

Despite being one of the 50 wealthiest Brits under 30 in The Sunday Times Rich List, O’Connor remains as happy to shop in Halfords — where she bought her “luxury six-man tent” — as Hermãs. She grew up, one of three sisters, in Brownhills, just outside Walsall, where her father worked in a welding factory and her mother in a nursery school. She remembers M&S as “the place we walked through to get to the shops we could afford”. But when she started modelling in 1996, having been spotted at the Clothes Show Live in Birmingham, aged 18, she suddenly went from travelling in the back of the family’s bright green Ford Cortina to being flown and chauffeured round the world.

“I found it difficult to get my head around it,” she admits. “I would sit in the front passenger seat; it didn’t feel natural to sit in the back. My driver, Vic, became something of a father figure; really it was almost like my father picking me up from the disco. He’s become a good friend of mine. We always chat for England andI catch up on all the politics.”

A “reluctant workaholic”, O’Connor will be back from modelling assignments in South Africa and New York just in time for London Fashion Week. Then she’s hoping to take the Grande Punto for a spin. “We’ll take our mountain bikes and put them on the back,” she says. “My mother picked up two lovely gel-padded seats for them because she says I’ve got a boney arse.”

For now, though, it’s back into a nondescript grey people carrier with Vic, and onto the next appointment.

On her CD changer

At the moment I like to listen to Pixies, Stevie Wonder andFranz Ferdinand