Gisele Bündchen has definitely already arrived. As I approach the photographer’s studio, her voice, a boisterous mix of guttural and singsong, bounds out of the open door and trots down the street outside. She is having her make-up done and, because her plane was delayed and she is late, she is multitasking. Publicists ply her with questions about her schedule; stylists present her with outfits: she handles them all easily. Wrapped in a soft grey top and leggings, she is a kinetic, shape-shifting ball of small balletic movements, sudden exclamations and lip-chewing.

She has come direct from a transatlantic flight, but her skin says she is just in from the beauty parlour. Of all the gorgeous girls in Brazil – and Brazil arguably contains more of them than anywhere else – Bündchen is a nonpareil of gorgeousness. Rolling Stone magazine, no stranger to hot numbers, couldn’t resist calling her “the most beautiful girl in the world” when it put her on its cover a few years ago.

The Swiss watchmaker Ebel has flown this hot number over to be shot by Style, and its marketing guy is giving her some company background, which Bündchen is repeating with cheerily gung-ho professionalism. “The brand was founded in 1911. It’s maverick and great quality! It’s classy, and I love class! And it’s reliable – you know what I mean?”

An hour later, she is doing what she does best. In front of a camera – slamming her body against the back of the set, arranging herself over a giant white sofa, manipulating her mane of hair as if it were an extra limb – she sneezes out pictures like other people send e-mails. The tiny red dress is by Dolce & Gabbana; the shoes are vertiginous Louboutins. On the speakers, Amy Winehouse complains mournfully: “You always go back to her.” Bündchen looks better in that dress than anyone else would. Sure, there are lots of pretty women on the planet, but here, at this moment, I would challenge any man not to go back to this one.

Born one of six sisters in the countryside of southern Brazil, Bündchen spent much of her childhood riding horses. When she began modelling, aged 14, she was out of step with the dominant Kate Moss look of the time, but she appeared on the catwalk for Alexander McQueen in 1998, and by the time American Vogue put her on the cover in 1999, with the cover line “The return of the sexy model”, everyone wanted to work with her.

“For me, I go to work, I have hair and make-up, and it’s like playing dress-up, like playing a character, you know?” she says between shots. “It’s part of my life, but it’s not my life. I’m a jeans-and-T-shirt kind of girl. I could never talk about fashion with my friends.”

She likes her men American and clean-cut. After five years with Leonardo DiCaprio, she now steps out with the American-football quarterback Tom Brady. The two were put in the spotlight late last year when Brady’s ex, the American actress Bridget Moynahan, found that she was pregnant two months after the couple had split up, and Brady had just started seeing Bündchen. It was all rather difficult, and remains so: Bündchen has been unfairly branded a homewrecker, and Brady reportedly left the hospital in tears after the birth.

Other than headlines, a personal fortune of £35m, residences all over the place, including a new pad in New York, and all the barefoot holidays on Brazilian beaches you could want, what does being the most beautiful girl in the world get you? I hope she will say it makes you feel fabulous about yourself all the time. “Of course not!” she says. “You never see yourself in that way, right? Everyone sees themselves in the morning and thinks, ‘Oh God, look at me. And today I have to take a picture, for God’s sake.’ Everyone has those days.”

It was some time during the DiCaprio years, on one of those days – the sort, as she once put it, “when you want to rip your own skin off” – that Bündchen did a Britney and shaved her head, before running back to her family to wait for it all to grow back. Being the most beautiful girl in the world could feel like a cage when you aren’t the happiest girl in the world.

She “retired” from the catwalk in 2001 to concentrate on ad campaigns. Last year, she earned £16m. Her last contract with Victoria’s Secret – before she and the lingerie brand parted ways – was said to be worth £2.4m a year. Now, at 27, she is learning to enjoy the fruits of a triumvirate of natural blessings, canny decision-making and an obsessive work ethic. “I began to wonder what it was all for. From 14, I had been going, going. Always getting up at 6am, always on planes, never any time to myself. I was a workaho . . . ” She stops herself. “I had so much to prove. Now I have time to find out who I really am and what I care about most. And I am a lot more calm.”

If you are also thoughtful and soulful, here is what being this beautiful gets you: a slice of freedom to be good. She is known to donate 5% of her earnings to charity. Some of the proceeds of her sandal collection, Ipanema Collection by Gisele Bündchen, go to charity – this year, an Amazon conservation trust. “I do a lot of different things, but I don’t go around and talk about it,” she says. “There are so many things to worry about. Animals are being killed; global warming is happening like crazy; there are children starving all over the world, not only in Africa. But if you talk about something, you have to understand what you’re talking about.”

So, there is more to Bündchen than her looks, which is perhaps why the clever, handsome, big-shot ecoboy DiCaprio, who has declared that he likes “down-to-earth girls” – and, make no mistake, fair-faced ones, too, since he is now dating the lithe 22-year-old model Bar Refaeli – went out with her for five years, not five weeks.

Back home, she is the preeminent female icon. Everyone wants to be her. Small children cried when they couldn’t get into the one show she appeared at during the last Rio fashion week. There are 36,000 boob jobs done each year in Brazil, and Bündchen must have something to do with a proportion of them. (The authenticity of her own lush bosom, has been a subject of fashion-industry debate for years – some make-up artists and stylists have felt them, but, curiously, no resounding conclusion has ever been reached either way.)

Bündchen’s response to her elevated status is to meet key members of the Brazilian press once a year for a Q&A session, the results of which are automatically deemed to be of immense national significance. This year, the theme ended up being contraception: “How is it possible to not want for people to use condoms and not have abortions? It’s impossible,” she was quoted as saying. The Catholic country was in uproar.

“Oh God, yeah!” she says now. “When I think things, I tend to say them. I’m an opinionated person, you know? There are a lot of sexually transmitted diseases, and I’m not going to say, ‘You shouldn’t use contraception.’ I think it’s important. I use it! I’m aware of my responsibility, but really I am like everyone else, and my opinions are just mine. There’s no reason why I’m more right than anyone else.”

This is the same openness that, earlier this year, moved her to declare that she didn’t like British men. “I don’t like them, and I wouldn’t even be able to tell you why not,” she said, claiming not to have the foggiest idea who James Blunt was.

And Bündchen can talk – oh, yes, she can talk. So much so that our allocated time ends and I’ve asked her almost nothing. Rather lamely – and, okay, possibly to provoke her – I ask what she thinks of suggestions that she and Brady are the Posh and Becks of the Americas. She throws back her head in horror. “Nooo! That’s crazy! I don’t know who said that. My job is my job and my private life is my private life. They have nothing to do with each other. My job is public, and it’s important to have something for yourself. If you don’t, you go crazy.”

Bündchen goes back to doing her dance with the wind machine. “Those top girls have a special something. If I knew what it was, I’d bottle it,” says the hair stylist, Sam McKnight. “It all just works. It’s the way they hold themselves, the face, the body, the hair. But there’s also a haunting mystery. Something extra you can’t quite nail. Power and vulnerability at the same time.”

Later, at the Ebel press conference, after dutifully flirting with Thierry Henry for the cameras, Bündchen takes on the striker in an impromptu penalty shoot-out. And what do you know? She wins.

Explore Women

• Fashion

• Beauty

• Diet & Fitness

• Relationships

• Families

• Celebrity

• Body & Soul

• The Way We Live

Times recommends

• The dirty weekend guide to Europe
• Sharing the McCanns’ hell
• Steve Coogan, weathering the storms