Naturally, lunch with Mario Testino, the world’s most in-demand fashion photographer, does not take place at lunchtime. “I’m here one day,” says Testino. “Tomorrow I go to New York, Thursday I go to LA, Saturday I go to Milano. What am I doing in LA? I shouldn’t be talking about that. The last two days I was in Capri. Before that I was two days in Venice, and before that I was a week in Paris.”

Testino is beyond jet-lag. He’s wearing a purple shirt by Versace, and white jeans by Acne – the sort of thing you’d wear at a beach party in the south of France. He is tall, lightly tanned and not skinny but more or less fit. He has said that he was “a big party person” and frequenter of nightclubs until his mid-forties when he realised that he “looked like the bouncer”. But, for a 54-year-old, he is quite youthful-looking.

It is late afternoon and our lunch takes place in the Peruvian photographer’s London office, in Holland Park. We are in a huge, almost bare room with white walls and a wooden floor. At one end are a chair, a bench and a coffee table – Danish furniture from the 1960s. On the little table is a picnic lunch: olives, nuts, ham, bread, pâté, and a bowl of crudités.

Testino is not hungry. Or perhaps he is. He pops an olive into his mouth. His life is a series of photoshoots, followed by parties, followed by luxury hotels, followed by flights. He must be offered more canapés than any man alive. What he loves, he tells me, is Japanese restaurants in Los Angeles. He worries about his weight. “My problem”, he says, “is that I like food.”

He loves Peruvian food too and when I tell him I don’t know much about it he gets excited. Testino is always excited; it’s one of his talents, and a big part of why he is so successful in the world of fashion and celebrity. He is relentlessly positive. His pictures of women make them look like ideal versions of themselves. He seems to give them a little bit of what they lack. Testino made Princess Diana look innocent and girlish; he gave Jennifer Aniston an edgy sexuality. “She had just split up from Brad Pitt,” he says, “she was like poor Jennifer and I was like ‘I’m going to make you so hot’.”

He puts another olive in his mouth. Peruvian food, he says, returning to the subject, is “the most undiscovered secret that I know. It’s where you eat best – apart from Italy.” Chefs from his favourite LA restaurants have spent time in Peru, he tells me. “There’s a lot of seafood. You know ceviche? That’s from Peru. It’s fish marinated in lemon juice, with chilli and raw onions. And then there’s tiradito, which is also fish marinated in lemon juice, but without the onions.”

THE MAN BEHIND THE LENS

How Testino changed fashion

One fashion photographer takes centre stage in the recent documentary film about American Vogue magazine, The September Issue: Mario Testino, writes Nicola Copping. Charged with the task of transforming a “toothy” Sienna Miller, in the words of the magazine’s steely editor Anna Wintour, into “fashion’s feistiest icon” and cover star, he grapples with a Roman backdrop of multicoloured mopeds and Vatican monks to create a shot worthy of the world’s most famous glossy.

Mario – one name suffices, such is his celebrity – was the only man for the job. Not only does he possess movie star magnetism, and look as good in front of the camera as he does behind it, with his Latin-American wide-smile charm, but his ineffable knack for making the mundane look majestic makes him the photographer of choice for fashion editors, designers and marketing managers alike. Whether shooting a Burberry campaign that features a suddenly sexy Emma Watson, or converting a gaggle of Camden punks into the essence of desirable London cool for the latest edition of British Vogue, Testino’s lens manages to turn hard lines soft, transform nervous subjects into new best friends, and create a world we’d all quite like to be a part of.

In doing so he can claim to have changed the face of fashion. Where Cecil Beaton portrayed the world of style in an untouchable, artistic light in the 1930s, 1940s and 1950s, David Bailey chose to expose its exoticism and decadence in the loose-living 1960s, and Helmut Newton favoured a stark eroticism in the 1980s, Testino became, in the 1990s, the photographer who captured women as women, rather than otherworldly objects. A decade on he remains the antidote to the cerebral conceptualism of contemporaries such as Nick Knight and Tim Walker.

It was in 2002, when the Royal Academy staged an exhibition of Testino portraits, that those beyond the fashion industry really began to understand his charm. The celebrities and models on show looked better, happier and more approachable than they’d ever looked before. As the Brazilian supermodel Gisele Bündchen puts it, in her essay for Testino’s latest book, MaRio de Janeiro (Taschen): “We understand each other. You know what I mean? I understand what he wants and I think he understands what I want. He is very respectful of my boundaries, and yet at the same time no one pushes them like him.”

Nicola Copping is the FT’s deputy style editor

He looks at the table. No, he won’t have any wine, he says. Later, he has to attend a fashion reception. Later? In fact, pretty much right now. Actually, he needs to shoot off in about half an hour. Or possibly 40 minutes. His life, which is arranged for him by assistants on several continents, is measured out in small increments – an hour here, a couple of hours there. Before he takes a flight, he needs to know how many pictures he must get out of the next shoot. It’s usually five a day.

“I’m a workaholic, I guess,” he says. What drives him? “I think doing drives me. I like to do.” When I ask him where he spends most of his time, he says: “God – that’s what I ask myself every day.” His main residences are in London and LA. “I keep trying to go more to South America,” he says, but he “hasn’t found a way of making it work, workwise”.

He has, nevertheless, just done a book on Rio, catchily titled MaRio de Janeiro Testino, full of pictures of parties and fabulous-looking mayhem. “This is the most unbelievable experience I’ve ever had,” he says, showing me the book. “People half-naked and sweating and so hot and loud.”

He’s always thinking ahead, always calculating. As a schoolboy in Lima, his best subject was maths. In fact, he was a bit of an outsider at school, not a popular boy. So he understands people’s frailties – and that, I reckon, is the force that generates his work. “When I started taking pictures,” he tells me, “I didn’t realise what I was doing. When I think of it now, it’s a human thing – like, if you see somebody in need, you go and help them. Or if you see somebody who doesn’t feel so good, you try and cheer them up.”

For instance, when he took a set of pictures of the reality TV star Jessica Simpson for Vanity Fair earlier this year, he knew how to make her look good. “I was touched by the fact that people were criticising her for putting on some weight,” he says. So he made her look statuesque, in a good way – as if this were a picture of someone who has been revered for years. He gave her class.

Similarly, his lovely pictures of Meg Ryan 10 years ago. There she was, in her late-thirties, perhaps fearing that her best work was behind her, maybe wondering if she’d lost a tiny bit of that smart-but-pretty vibe that made her famous. And what does Testino do? He makes her look fresh and girlish, lying on her stomach, kicking her legs behind her, her face covered in light. Meg Ryan as platonic ideal.

“I have a really funny memory of Meg,” he says. “I couldn’t recognise her in my pictures. I tried everything, and I couldn’t recognise her. And she saw me struggling.” It was Ryan herself, he says, who suggested bathing her face in light.

His picture of Julia Roberts has her holding what appears to be a stuffed squirrel. At last she looks interesting, or at least peculiar. Then there are his pictures of Kate Moss. Over the years he has made her look like at least 10 different people, each equally intriguing. She looks by turns intelligent, witty, arty, innocent – nothing like the party animal portrayed by the tabloids.

Testino explains: “As a photographer you either take the picture for yourself or for the person you’re photographing, or the magazine you’re working for, or the company whose advertising you’re trying to communicate. You either make the picture look like you, or you make the picture serve the purpose of that client by emulating them. If I’m working for Burberry, I’ll try and make it look like a Burberry girl, a Burberry moment. If I’m working for Versace, I’ll probably go in the opposite direction: I’ll try to make it Versace.”

He seems to photograph more women than men. In fact, compared with his women, who look like goddesses, some of his men can seem a bit shifty and dysfunctional. His picture of Bono and Naomi Campbell looks like a madman clutching a princess. Mick Jagger looks like a drunk singing a song in a pub. Princes Charles, William and Harry, photographed together, have mad-looking grins. Oh, but the actress Kirsten Dunst looks like an angel, and the supermodel Gisele Bündchen looks so gorgeous she might be not quite of this world.

“Women are alien to us, because we’re not women,” Testino tells me, man to man. “Women”, he adds, “are much more protected, judged, looked at, appreciated, mesmerising than men are.”

He eats another olive. They have been marinated in chilli oil, and some have been stuffed with tiny hot peppers. I have some of the Wiltshire ham.

Maybe, Testino thinks, we respect women more because of our relationships with our mothers. “Women are much more open to trying different things than men are. I find that men will get an idea of themselves, and will stick to that idea, much more than a woman would. A woman can say, ‘Yes, let’s try it!’ Maybe because women become mothers eventually ... they are more accepting about possibilities.”

Maybe. After leaving school, Testino studied law and then economics at the University of Lima. Then he moved to the US to study international relations at the University of California, San Diego. In 1976, he changed direction again, and moved to England and worked as a waiter. It was then that he began to take photographs, carrying his portfolio tirelessly around glossy magazine offices.

Testino says that his big artistic breakthrough occurred in the 1990s, when more women worked and, consequently, saw themselves as doers, rather than people who lunched and drank cocktails and had tea parties. He got in closer to create versions of women that looked less posed – “bringing out the real woman”, he says, “rather than turning her into a fake thing”.

He tells me about the first time he photographed Madonna, in 1995. She arrived at the Chateau Marmont – the hotel in Hollywood where he practically stayed for two decades – with her hair scraped back and tied in a ponytail. And he thought: she looks pretty good as she is. No need to get her all done up.

With Diana, he says he felt pretty weird talking to her on his mobile. “I would turn away, almost as if people could hear.” But he managed, in the famous pictures he took for Vanity Fair in the summer of 1997, to depict her as nobody had managed to since she’d become a global icon. He did it, he says, by imagining her as the “normal girl” she was before she met Prince Charles. And he’s absolutely right: we look at the pictures, and that’s what we see: amazingly, she’s a normal girl. She died a few weeks later.

Testino hangs out with famous people all the time but he’s not quite a celebrity himself; he values his privacy. When I ask him if he’s in a relationship, he thinks about the question for a while, and then declines to answer. “I never like to talk about myself,” he says.

And now he needs to go. People are getting ready. Cars are being ordered. Somebody is bringing a jacket. Testino keeps talking: about the subject of the fashion world’s obsession with skinny girls, on which he is absolutely clear. Models, he says, are teenagers. Teenagers are skinny. “It’s normal! When I was 16, I was skinny. And the reason why designers hire these girls ... is because clothes just look better on a skinnier person. For the simple fact that the outfit moves.”

Another olive? A carrot stick? No, that’s it for him. “The moment people like us, or anybody that’s a little bit chubby,” he continues, grabbing the sleeve of his shirt and pinching it tight, “nothing moves. Things are clinging on to your fat. So it’s hard to do a fashion story on somebody that’s like that.”

Then his jacket arrives and he’s gone to talk to women in fabulous dresses and, no doubt, be offered lots more canapés.

‘MaRio de Janeiro Testino’ is published by Taschen (£27.99) on September 25. To order a copy for £22.39 plus p&p call the FT Bookshop on 0870 429 5884 or go to www.ft.com/bookshop

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Mario Testino’s studio
Holland Park, London

Fortnum & Mason Outdoor Feast hamper (serves 2)

Mixed fresh olives
Carnevale nuts
Handcarved Wiltshire ham
Pork rillettes with crusty bread
Poached salmon portions
Large chunk of chicken mozzarella and tomato pie, with crudités of celery, carrot and cherry tomato
Fresh strawberries and mint
Cupcakes x2
Bottle of Viognier
Bottle of Blenheim still water x2

Total £85