Oh, God, it sounds really, really clichéd, but it was honestly a total surprise,” says Lily Donaldson of the moment, six years ago, when an agency scout stopped her on the street in Camden and asked her if she’d like to be a model. “Yeah, whatever,” I honk, sizing up her perfect features. “Because it’s not like you’re beautiful in an obvious way or anything.” She laughs, her divine mouth lifting at the corners, then decides to plough on. “No, seriously, I’m not just saying it. I swear on my life, I never thought of myself like that.”

Obviously, I’m not buying it — and neither is anybody else. Though you may not know the name, Donaldson, 22, has ranked among the world’s most successful — and highest-earning — models for five years now. Dior, Burberry, Dolce, Lanvin... Actually, the list of fashion houses that haven’t booked her is much shorter than the list of those that have. Amazingly, she achieved all this without looking like most of the alien waifs who drag their feeble carcasses up and down the catwalks. Yes, she is micro-hipped and very tall (surprise, surprise). But there’s a Bardot-like sumptuousness to her features and, now she’s no longer a teenager, even the semblance of a woman’s body. In short, she is beautiful, but also hot. The sort of girl you could plonk down in the middle of an All Bar One on a Friday night and watch the boys go gaga.

So, why isn’t she a household name? She may be royalty on planet fashion, but she has nothing like the recognition factor of Agyness Deyn or Lily Cole (though a stylist friend tells me she is “far more in demand, work-wise”). Perhaps it’s because she isn’t kooky-looking. Or that, while perfectly chatty, she’s rather low-key. For example, I turned up to meet her at a studio in east London and was nattering to one of the fashion team for ages before I realised Donaldson was standing right next to us, in duffed-up sneakers, top with holes in it and zero make-up. She carries herself shyly and is softly spoken.

That said, her ascent was a given. Donaldson’s isn’t some rags-to-riches tale of a gas fitter’s daughter from Warrington who was spotted against all odds in the local chippy. She was brought up in boho privilege in north London (father a photographer, mother beautiful and slender) and went to Camden School for Girls, where if you look like Lily and hang around the school gates long enough, getting discovered is a bit of a cert.

She was only 16 at the time. “My first-ever show was so scary,” she recalls. “I was there an hour early, terrified. I had to ask the make-up person, ‘How do I walk? How do I walk?’ Suddenly it seemed so complicated.” She laughs, fully aware of how ridiculous a model fretting about her strut sounds. Donaldson is conscientious. She believes that a lot of time and money go into flogging clothes, so you should take it seriously. “I really respect this job. Look at today, all these people working hard,” she says, gesturing to the dozen or so crew. So, the millions you’ve made notwithstanding, you don’t regret leaving your normal life behind at 16? “I didn’t miss my childhood,” she says. “I stayed in London for a long time [after I was signed]. I wanted to hang in the park with my mates, drinking cider, and so I did.” And school? “I finished my GCSEs and was going to do art, philosophy and history A-levels,” she says, “but whatever. I’m learning a lot. It may not be from textbooks, but it’s an education. Christopher Bailey, John Galliano — they’re artists. And I feel involved. To a certain extent, of course, you’re a blank canvas, but if you’re just that, if you don’t perform, you won’t get very far. I have to portray other people’s dreams.”

She likes the simplicity. No Fashion Cafe or novel-writing aspirations for this girl (thank God). She doesn’t even like the celeb side of the job, so has largely avoided media scrutiny. “I don’t know whether it’s because I don’t find it interesting, or maybe it’s because I’m not very interesting, but I am glad not to get the attention. It helps that I moved to New York. People are, like, ‘Whatever!’ there. There are thousands of models. It’s a city full of them.”

In fact, the nearest she came to tabloid scandal was last summer, when news broke she was dating Michael Phelps, the Olympic swimmer. The story was entirely false, yet dogs her to this day. “I’ve never got to the bottom of how that started,” she says, giggling. “I’ve literally never met him. I’d like to meet him, actually — the big, swimming fish-man.”

In fact, at the time, she was dating Vladimir Restoin-Roitfeld, the son of Carine Roitfeld, editor of French Vogue. They’ve since split up, but she won’t tell me who, if anyone, she’s seeing now: “Oh, I’m sure your readers don’t care who I’m dating.” (Fair enough — you probably don’t.) She will say that she hangs out a lot with other models, mainly Raquel Zimmermann and Caroline Trentini, and likes to throw impromptu picnics in her car during the shows.

“You should see my car in Milan. It’s like a deli. My driver thinks I’m completely insane, making sandwiches in the back with pots of honey.” Hmm. Is this the classic “model casually drops into conversation how much she eats” moment of the interview? Since she brought it up, I tell her she’s looking less thin than she used to. “I’m older now,” she says simply, “and I was born this way. I could show anyone a picture of my mum and they’d be, like, ‘Oh, I get it.’” I wasn’t suggesting you had an eating disorder, I say, though others on the internet have. “Oh, I know, but I was 17, 18. C’mon! My metabolism was running high, and I always lose weight during the shows.”

So, what’s next, I ask? With the cruel cut-off age, you must be thinking about what you want to do in the post-Prada world? “Are you saying I’m getting on, then?” she asks, mock-gasping. I’m guessing you’ll be set up for life on the money you’re earning? “Well, I’ve got a good business manager — thank God for that — and I’m not a big spender. I’ve got T-shirts I’ve worn since I was 14 and I still wear them. Look at this,” she sighs, yanking at her top. “It’s got holes in it. But I’m happy in what I’m doing now and I hope I can do it for a few years more. It took a while for me to get really into it, to feel comfortable, that this is my job. Now I’m proud to say I’m a model. Why not, right?” Why not, indeed.

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