It's Sunday night in Paris, creeping up on 10 o'clock, and the mood is tense. Cara Delevingne, the girl everyone wants a piece of right now, is pacing a hotel room in her underwear, talking to her agent on the phone. Outside, an agency car is waiting to take Delevingne to a last-minute casting out in the twentieth arrondissement.

On the bed, there's a key look from the Spring ’13 Christopher Kane collection, which Delevingne is meant to wear to a party under way on the other side of town, in Saint-Germain.

"They hate me," she tells her agent. "I know they do! It's pointless. They're never going to cast me in that show."

Delevingne storms into the bathroom. When she reemerges, phoneless, about a minute later, she looks grim. She shoots a glance at the Kane look so seething, you half expect the dress to disintegrate or burst into flames. But it doesn't, so Delevingne leans against the wall, staring at it, sucking on her cheek and thinking. If she puts on her jeans, she's going to the casting, which is almost certainly a waste of high-value Paris fashion week time; if she puts on the dress and heads to the party, she'll not only be pissing off at least half a dozen industry VIPs, but she'll also be signing up for a long night of air-kissing, small-talking, and posing for photographs, which is its own kind of hard work. Also, she's really not that keen on the dress, which is made of rubber.

"I can't," she says at last, scrunching up her famous caterpillar eyebrows. "I just…I can't." And with that, Delevingne goes back into the bathroom. This time, she shuts the door.

The buzz around Cara Delevingne crescendoed to a roar this season. She walked thirty-nine shows, including those of such heavy hitters on the fashion calendar as Marc Jacobs, Burberry, Dolce & Gabbana, and Chanel. She seems determined to rank with the mainstays of the catwalk circuit. And yet the question lingers: Why? Delevingne is extraordinarily pretty, with sharp, doll-like features, but she's small, and unlike her friend Karlie Kloss, she wasn't self-evidently engineered by God to walk a runway. Nor, for that matter, is Delevingne one of those girls who endures blisters and 5 a.m. call times because she's got fifteen siblings to support back in the recently democratized country she calls home, or because modeling is her one chance to get out of her hick town, date a rock star, and see the world. Not hardly. Cara Delevingne would be famous, or almost famous, or about-to-be famous, even if she'd never modeled at all.

"This is where he kept the gorillas," Delevingne says, opening the door to a book-paneled study in London. "Can you imagine a gorilla in here?" She makes a monkey face and does a little monkey dance, and then resumes her tour of the £10 million town house in Belgravia where she was raised. The house has a backstory: It once belonged to John Aspinall, a society playboy whose passions in life were high-stakes gaming, from which he made his fortune, and cavorting with wild animals, in pursuit of which he spent it. It's tempting to suggest that his spirit lives on in Delevingne. That of her own father, Charles, might account for some of her wild streak, too. Of the property developer, Tatler wrote that he "wears his lime-green Versace suit whenever the dress code allows." The Delevingnes' current wealth and social standing derive in part from Charles' holdings and in part from the extended family: Cara's maternal grandfather, Sir Jocelyn Stevens, was managing director of the Evening Standard and Daily Express in the sixties, and her grandmother, Janie Sheffield, a lady-in-waiting to Princess Margaret.

Cara still resides in the family home—to the extent that she resides anywhere these days—occupying a few shambolic rooms in the basement. The house tour includes a visit to her drum kit and a closet filled with high-tops, as well as a rifle through Delevingne's collection of animal costumes. She zips on a panda-bear costume. "I like to wear it around the house," she explains with a shrug.

The tour continues. There's a stairway decorated with group portraits of Cara and her sisters, Chloe and Poppy. Chloe, 28, has a members' club in South Kensington named after her. Poppy, 26, is a former model and Chanel ambassador. Both are tall, lithe blondes who take after their mother, Pandora, a scene-making London beauty back in the seventies. "Look at these amazing tits," says Delevingne, holding up a framed eighties-era issue of Tatler. Pandora is on the cover, wearing a low-cut swimsuit. "I'm still waiting for mine to grow in." She ducks a look under her panda costume. "Nope," she adds. "Not yet."

Cara Delevingne is a ham. If you accuse her of being an It girl, her eyes will cloud over, and her dainty jaw will set, and you will never be her friend. If you call her the next Kate Moss, or the new Twiggy, she'll sneer and ask what she's got in common with either of them, aside from the fact that they're all English and waifish. If you tell her she's beautiful, she'll roll her eyes. But the ham thing—that she'll cop to.

Another night chez Delevingne:

"The thing I like about doing runway is that I can't fuck up. I mean, if I fall, that's the one situation I can't get out of by making jokes or funny faces. You know, a big old song and dance. Which is what I normally do when I get into trouble."

Delevingne sucks on a cherry tomato. "Actually," she continues, after a comedy beat, "that is probably what I'd do if I fell at a show. I wouldn't know how to stop myself."

Models aren't supposed to be hams. Silly faces aren't "aspirational." But Delevingne can't help it—she's constantly performing. She's performing when she's mugging for her pals backstage at shows, and she's performing when she's on the runway, too, pretending to be what she actually is: a model. To watch Delevingne walk is to witness a satire of catwalking—her eyebrows knit in an expression of deep and serious focus, her spindly legs making an exaggerated stomp. Or maybe satire is the wrong word. It's more like a dramatization, Delevingne's walk. Self-aware but getting into the part. That meta-walk is how you know that Delevingne is acting.

And that's how Delevingne sees herself: as an actress. Feel free to roll your eyes, but she is convincing on this point. Delevingne studied drama at Bedales, the arty boarding school in the Hampshire countryside that also counts Juno Temple and Alice Dellal as recent alumni. While at Bedales, she auditioned to play Alice in Tim Burton's Alice in Wonderland, and got close enough to the part that she met with Burton about it in person. When she first started modeling, and was day-jobbing as an e-commerce girl for Asos, it was to raise money for drama school. (Lodging aside, Delevingne contends that her parents stopped supporting her at 16.) And Delevingne is at her loosest when she's talking about the kinds of characters she'd like to play—the ones, she says, that will give her the chance to "go mental." In the meantime, she's made a very satisfactory feature-film debut, playing an aristocratic beauty in Anna Karenina. By her own admission, she didn't have much to do in the film besides look pretty—a job for which modeling had amply prepared her.

"It's messed up, though," she proposes, "because modeling makes you so self-conscious, which is exactly what you can't be when you're acting." She slumps back and gathers her thoughts. In general, she maintains a furious conversational pace, but what she's about to say is important to her, so she takes her time.

"It's like…I never cared what I looked like. I honestly never did. And I never wanted to do 'pretty girl' parts; I wanted to lose my shit, or be funny, or play some fucked-up rabid wolf child. In school, I was Martha in Who's Afraid of Virginia Woolf? I loved that. But modeling…"

She pauses here for more thought-gathering.

"When you model, there's no way you can't notice yourself. Do you know what I mean? Because you're constantly surrounded by people saying, 'Oh, she's too short, she's too skinny, she's this, she's whatever.' And you're right there. They're talking about you and you're right there. And…"

Delevingne stops again and sizes up her audience. She surmises that a tale of modeling woe is not going to play well and corrects course. "What I mean is, I've gotten less confident. But I've gotten better at acting confident." Your heart goes out to Cara Delevingne, kind of. She's too blessed to feel sorry for, and you do wonder whether her admissions of vulnerability aren't part of the show. That would make for an awfully canny performance from a 20-year-old, but Delevingne seems up to it. She's a clever girl.

Too clever to be believed when she professes that this whole modeling thing is just a giant wave that's crashed over her and that she can't do anything to keep it from pulling her out to sea.

It's not that Delevingne is untruthful. Spend a day at London fashion week with her, shuttling from castings to fittings to shows to parties, and you will appreciate that she is overwhelmed. The demands on her time are enormous. So too the demands on her mental and emotional energy, what with all the command performances: Cara the ham, Cara the meta-model, Cara the rebellious wild child. But she's embarrassed by her own ambition. Again: Cara Delevingne walked thirty-nine shows this season. Why? "I guess, you know, modeling is the thing I can do well at right now," she says, when pressed. "And I do want to do well. Why would I want to fail?" Failure is unlikely. Plucked from Asos obscurity to walk the Fall ’12 Burberry Prorsum show, Delevingne has spent the past year and a half rapidly ascending fashion's heights. She has a contract with Burberry and has starred in numerous campaigns for the brand, including the latest for Burberry Beauty. She's been shot by the likes of Inez and Vinoodh, Alasdair McLellan, Bruce Weber, Mario Testino, and Terry Richardson. When Delevingne leaves a fashion show now, she's the model getting scrummed by photographers.

When it's all happening—when the flashbulbs are going off and there are fans yelling her name—it's pretty clear that Delevingne is enjoying the attention. It's only later, when you ask her about it, that she gives voice to qualms. "What bothers me, I guess, is when I get these messages from girls on Twitter, and they're like, God, you're my idol, I really admire you," Delevingne explains. "It's like, Admire me for what? What have I done? It's not that being in a Burberry campaign, or walking in a Chanel show is nothing. It's just…I know I can do more."

Cara Delevingne really, really, really hates being called an It girl. And she's got a point: The term is so diminished, so wasted on disposable daughters-of and DJ-slash-whatevers, that it's insulting to apply it to a girl who does, genuinely, have It. And whatever It is, Delevingne has got it in spades. She exudes a particular anarchic energy that strikes a chord with the times, and that's why people are fascinated by her. It helps that she's gorgeous. But Delevingne is that rare model who is noted less for what she looks like than for what she embodies and who she is. That's why girls write to her on Twitter. Delevingne's It-ness is hard to define. But here goes. First, let's stipulate that family matters. The Delevingnes are a clan known for both their good looks and their bonhomie. They are excellent at going to parties. Further: There are associations with royalty going back generations, but the Delevingnes themselves are not aristocrats. In England, these fine distinctions matter. Cara Delevingne can hang with the high and mighty, but she's still an everygirl. It's the Kate Middleton trick.

Friends matter, too. Delevingne's bezzie mates, such as Adwoa Aboah and Clara Paget and Mary Charteris, comprise the young, cool set in London at the moment. And if that hadn't been enough to project Delevingne into the zeitgeist, then her rumored romance with One Direction heartthrob Harry Styles certainly did the trick. (All Delevingne will say on the subject of dating is that she doesn't feel she can be relied on in a relationship right now, a comment that is at once remarkably opaque and undoubtedly true.) There's some other stuff that builds the Delevingne legend, too, like the fact that American Idol creator and former Spice Girls manager Simon Fuller invited her to write songs with his producers when she was 17. (She still has the demos.) But nothing fully explains the Cara Delevingne mystique, or its power. She's been anointed the face of youth culture today, and no one, including Cara Delevingne, is exactly sure why. Delevingne is a riddle even to herself.

Which might, in the end, be the cause of all her hemming and hawing about being a model, and the reason she approaches the gig in such a self-aware and performative way. It's impossible to manage an allure you don't understand. And it's difficult to take credit for that allure, or not to fear that it will suddenly abandon you. It's no wonder Delevingne likes to walk a runway: Either you make it to the end and back without falling, or you don't. It's in your control. Being an icon: Not so much.

Another night chez Delevingne. Cara fixes an avocado salad and sits down at the kitchen table. To make room for her plate, she stacks her BlackBerry on top of her iPhone. "My dream," she says, "is to go spend a week on some island, with no phone." Only her mouth is full of avocado, so the dream comes out sounding, more prosaically, like this: To spend a week on an island with just one phone.

"Yeah," Delevingne says, snickering, "even just the one phone would be OK. Not the dream, but OK."

Paris fashion week has ended. Delevingne walked Louis Vuitton, the last show, and flew straight to Sicily for a shoot; she arrived back in London late that afternoon and has another shoot first thing in the morning. Her schedule is unrelenting. But this evening, at least, she's got the house to herself and no one to answer to, and her guard is down. The next day she'll be modeling at a zoo, with spiders and spider monkeys. John Aspinall would be pleased. "God, I really hope there'll be snakes," Delevingne enthuses, in much the same way that more-average 20-year-old girls enthuse about the possibility of cupcakes. "I've always wanted to do a shoot with snakes—big snakes, like pythons." She does a little snake-charming dance and grins. Maybe it's all an act. But Cara Delevingne sure looks like she's having fun.

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