Yasmin Le Bon is at her new gig, and the runways of Paris, New York or Milan it ain’t. “You okay? Good, good,” she says, with real warmth, a girl’s girl. I’m ushered into one of those fish-tank meeting rooms that appeared in the 1990s.

She’s not wearing much make-up — well, none at all. Just a pink cardie, cotton drawstring trousers, a grey vest and bleached hair loose around her shoulders. “Sorry about these old hippie clothes,” she says — but they aren’t. She looks rather fresh in them.

To the side there’s a clothes rail bearing the fashion line she’s designed for the women’s high-street brand Wallis, our hosts. It’s the first anyone has seen of it. Exciting.

“So, yes... It’s for a woman like me. And I’m 44 — 45 in October. Might as well say it before anyone else does!”

Wow. Really? You could knock me down. I know Le Bon was working in the mid-1980s, but 45? Up close, all 5ft 9in of her, she’s not a day past 27. Her forehead has some reassuring little furrows two-thirds of the way down, and there are no visible signs of cosmetic plumping. How do you do it, I say, as I must. “Airbrushing,” she replies airily.

In 1989 — smack in the middle of the supermodel era — she was reputed to be the highest-paid model in the world. Now that group of ragingly fecund women are approaching the menopause. All, with a couple of notable exceptions, have completed the perfect supermodel triptych: giant career, marriage to smart, handsome alpha male, kid or kids. Le Bon pulled it all off first.

But what comes after that? Supermodels were never supposed to be 45. The Wallis gig — she’s contracted for an autumn/winter collection and one for spring/summer 2010 — has turned up at the perfect post-yummy-mummy moment. Wallis is cock-a-hoop at how she’s thrown herself into it, doing a regular three-day week at the offices on Oxford Street. “Yes, I’m here all the time. It’s given me a whole new purpose,” she says.

Anyway, top marks to them for choosing her. The brand had got a little dusty these past few years. Silly, really, considering how scandalously underserved the British fortysomething woman is on the high street.

“I have a normal-sized body, and if I feel comfortable with the clothes, then I’m hoping other women my age will too,” she says. “Something like this, for example” — she holds up a floor-length jersey dress — “could be worn at home, or on the red carpet with a military jacket around your shoulders. Or this” — she grabs a slippery wool minidress with a high neck and presses it up against herself. “You could put it on in the morning and not think about it again.”

No, ladies, Le Bon definitely won’t be sending you out into the world dressed looking cheap. Her style has always leaned towards the demure. “Azzedine Alaïa, Yohji Yamamoto, Jeanne Lanvin, Madame Grès,” she says when I ask for her favourites.

“As you get older, you get less confident about your body. It’s a strange moment when it starts to happen. I never thought it would at all, but it has. I’m still in shock about it actually. I’m covering up more than I used to. Luckily, I’ve always loved a high neck or a long skirt. I just think they’re chicer and sexier than you would imagine.” What a fine king’s consort she would have made. Elegant but never haute. Instead, she has been Simon Le Bon’s consort. You see them out together still. At this year’s Gorbachev Foundation ball, there they were. Simon, 51 soon, in his tux. Her, willowy in a green strapless dress. Staring at each other and laughing their heads off. They looked like a love story.

“How have we done it? Oh God, I don’t know. The old-fashioned things. If you marry for love, if that love’s really strong, you’ll get through the hard times.”

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