Presumably they do it to stop us keeling over with envy and to prove that fame and fortune haven't changed them a jot, even if we're thinking, 'Yes, but you travel in private jets.' True to form, Twiggy Lawson, the world's first supermodel, says she likes to do jigsaws, cooks a mean pumpkin and seafood Thai dish and wears trackie bottoms and no make-up when she stays in her weekend house in East Anglia.

However, there's no ignoring the fact that she's also been famous for most of her life. She's dined with Fred Astaire, been on the cover of a Bowie album and was photographed by Avedon and Bailey. Sir Paul McCartney is one of her best friends, which is certainly outside the realm of most people's experiences.

But normal is how she describes her life. "I'm kind of a boring, old, middle-aged, happily married woman, " she laughs.

Forty years after she was first splashed across the pages of the Daily Express as "the face of 1966", Lawson (christened Lesley Hornby), still has that gamine charm which catapulted her to worldwide, iconic status. Slim, blonde, sharply dressed in a navy trouser-suit and wearing giant, pink-tinted, designer shades, she wears her 57 years well and without the assistance of the surgeon's knife . . . but more of that in a bit.

She was in Dublin is to promote her range of bed linen, called Town and Country, stocked exclusively in Dunnes Stores. There are seven designs, which include pillowcases, throws, spreads, and cushions. Her favourite design is Provence, a kind of French toile in blue and green. "What can I say? It's fun, I love it, " she says of the project, and is quite a keen seamstress herself, making bedspreads and curtains in her spare time.

There are touches of the renaissance woman about Lawson.

Obviously, she models and her career got a new lease of life when she was chosen, alongside Laura Bailey and Erin O'Connor, to front a successful Marks & Spencer advertising campaign. But she's explored other avenues too, with varying success. She's acted on stage and TV and won two Golden Globes for her role in Ken Russell's film The Boyfriend. She was nominated for a Tony for her role in the Gershwin musical My One and Only, which ran for nearly two years on Broadway. During the '90s she donned the mantle of TV presenter, interviewing guests like Dustin Hoffman and Lauren Bacall on the ITV series, Twiggy's People. As well as the linen range, she also designs a range of clothes for a mail order catalogue company. And, she's one of the star judges on America's Next Top Model, alongside Tyra Banks. How, I ask her, does she prefer to be perceived? As a business woman maybe?

"I don't know, I've done all these different things because opportunities have presented themselves, " she says. "I didn't plan in 1966 to become a model. I was a schoolgirl. I wanted to go to art school and become a dress designer, which is funny because now I'm kind of fulfilling that in a certain way. I've always loved sewing. But you know the whole modelling thing was as much of a surprise to me as to the rest of the world, let alone becoming world famous for that look, and it's something I'll live with all my life. Whatever I do, nothing will eclipse that."

She doesn't resent being perennially associated with the '60s because, if her 1966 discovery hadn't happened, she would never have had the opportunity to try other things. "I was sweet; I was a funny little thing. I look at those pictures and I can see I looked very different to anyone else and it was fabulous. It changed my life but I'm much prouder of starring on Broadway for 18 months, in a major Broadway musical, and singing and dancing every night, " she explains.

While she's chatty and seems decidedly down to earth, she also gives the impression of shrewdness, a quality that has obviously served her well throughout her career. Was she hugely flattered when Balenciaga recently named a bag after her?

Not exactly. "Well, you know, they never got permission. I was a bit annoyed quite honestly and they're actually not allowed to do it." Is it an issue? "No, it's not an issue. I think they named a bag after Jane Birkin, didn't they? But they shouldn't legally do that, and if they do at least they could send me a bloody bag!"

Back in the heyday of Twiggymania, her image graced everything from lunchboxes to boardgames. Mattel made a Twiggy Barbie doll and there were "Forget Oxfam, Feed Twiggy" badges. Even today, Twiggy memorabilia is a huge seller and people would call her after returning from trips all over the world and tell her: "You'll never guess what I saw your face onf" But as she says herself, there were "no permissions, no royalties, no nothing". It's one of the reasons she started selling branded goods herself; there are now five shops in Japan which sell a range of Twiggy retro clothing.

"Rather than just let all these people around the world rip me off, we might as well do our own. And again, that's what led me to doing the bed linen. But I love it. I'm very passionate about fabric and beautiful things, so it's not just a matter of lending my name. I wouldn't do that if I didn't like it, " she explains. The Balenciaga bags might be posh but there are many firms out there who don't make such nice products.

"It's a pain in the neck because they're not very nice things and people assume that if you're name is on it, your face is on it, you've something to do with it and that ain't the truth."

She's enjoying her work on America's Next Top Model, where she most definitely doesn't play a Simon Cowell or even a Sharon Osbourne role. Tyra Banks is, she says, very lovely and very clever.

"When I went into it I said I'm not going to come on and be cruel because, you know, they're kids. But on the other hand, they know it's a competition, they know there's 13 of them and only one is going to win. I try and be as kind as I possibly can.

But a couple of times we had girls who are so in your face that sometimes you kind of want to say, 'Don't be so bloody pushy, you should be so lucky.'" While it's not like she's ever been completely out of the public eye, the show and the ad campaigns have introduced her to a brand new generation. "Yeah, but that happens, " she says.

"I've been in the business for 40 years, it's my 40th anniversary of being discovered. I've had, as every career has, moments when you're very in the public eye. If I go off and do theatre in America, and people in England think I've dropped off the face of the earth.

Doing the show means that she can't do much theatre at present and that's her first love. She also says that there aren't very many roles available for women of her age. "I'd love to do more films but that's tougher because it's a very tough arena and much bigger actresses than myself bemoan the fact that once you hit 45, it gets harder, " she admits.

Which leads on to the matter of her youthful appearance.

What does she think of plastic surgery, which is a slightly more subtle way of asking her what she's had done. "I haven't had anything done at the moment, " she says without hesitation. "I've got friends who've had work done, very good work done, and it looks great and I think, sure, if it makes people feel happy and they want to spend that sort of money. The only advice is make sure that they go to someone good. We've all seen the frightening ones." She's vehemently anti-Botox though. "It's botulism. Where does it go?"

Society's obsession with looking young confuses her. "There used to be this wonderful thing years ago: with age you gained a certain respect for your knowledge. They've got to find something else in their lives, it can't all be about what you look like. It can't, " she muses. "Although I started as a model and obviously what launched me into whatever was my looks. But I was a kid and the things I'm most proud of are the things I've achieved that are nothing to do with looks." Doing her stage performances took some degree of accomplishment, she hopes. Helen Mirren is a role model in this respect. "She's just a consummate actress and she's gorgeous but she hasn't had all that crap done to her face. She's just a brilliant, brilliant actress and a beautiful lady."

Of the current crop of models she thinks Kate Moss is extraordinary and a chameleon, but really, she doesn't know the names of very many models and she's out of the loop fashion-wise. Her thoughts on the recent controversy about underweight models are that in many cases, these are young girls with quick metabolisms. "You get a 17-year old who's 5'11", she's not going to be fat, " she points out. "When I modelled, aged 16 1/2 to 20, I weighed six and a half stone, but I was incredibly healthy. I ate like a horse. I was just a very young, skinny kid.

And I didn't really put on weight until my mid to late 30s because that was my metabolism. So I got hit a lot in those days for making kids want to be thin." Far more worrying she thinks is the rapidly decreasing size of Hollywood actresses. "They don't have to be thin. God bless Scarlett Johannson. She's gorgeous."

Two causes close to Lawson's heart are animal rights and breast cancer awareness. She can't help everyone, she says, so she's chosen the two that she feels most passionately about. "They're the people doing the work . . . it's just someone like me who can bring it to the public's awareness and it's nice to do that."

The interview draws to a close and I hate to admit it but she does seem very normal, although I can't agree with the 'boring' tag that she labelled herself with earlier.

But she is happily married. Her husband is the actor/director Leigh Lawson, who was formerly married to the actress Hayley Mills, and they've been together for 21 years, getting married in 1988 under a weeping willow tree. They've worked together on stage and on her skincare range, which is currently on hold. She has a daughter Carly, 26, an animator, from her first marriage to the late actor Michael Whitney, and a stepson, Jason, who is a theatre director.

One final question for her. What are her vices? "I'm very bossy. Ask my husband and my children. I think most women are a bit bossy, they have to be, don't you think? I think we should run the world."

And that's when you realise, that really, Twiggy Lawson is very normal indeed.