Alexa Chung is lying flat on the floor, one leg going up and down like a piston. She is demonstrating "an annoying ass exercise" (her words) that she does as a concession to fitness. "I can't go to the gym - it just doesn't look very fun," she says. "If I'm not doing a ballet class, I just do this a lot."
ou wouldn't catch Kate Moss flapping her leg around. Alexa is frequently compared to Kate, which is understandable: like her, she's one of the few celebrities who genuinely inspires women to buy stuff on the basis that she herself wears it so well.
But the two are also very different. Yes, they're both models with fiercely loyal female fan clubs, but that's where the similarities end.
Kate (born 1974) came of age in the Nineties, when being a brilliant model was enough. Alexa (born 1983) is equally a product of her time. As well as being a slashie (model/TV presenter/designer/nascent art director), she's a fully paid-up member of the digital age, with the requisite millions of Twitter and Instagram followers, something brands increasingly require to feel confident that they've chosen the right person to sell their products.
I imagine Chung cringes at the Moss comparisons and would be the first to admit that she is not in the same modelling league. But then, she doesn't have to be: the rules are different now. Personality is a big part of the package for models, and God help the boring ones. Chung might have a beautiful face, but it's her personality that's pitch-perfect: funny, self-deprecating and whip-smart.
She also has the starry friends (an eclectic mix including Poppy Delevingne, Daisy Lowe, Pixie Geldof and Nick Grimshaw), the proven track record of shifting units (2009's Alexa remains one of Mulberry's best-selling bags) and a personal style that constantly sees her on the best-dressed lists. Basically, she's got the lot, but wears it lightly - with a slick of Chanel lipstick, an Erdem dress and whatever handbag the rest of us plebs will want a few months later.
Possibly because she started her career as an interviewer (on Channel 4's Popworld in 2006), she is a more generous interviewee than most celebrities. The mask doesn't slip. The eyes don't glaze over. There is no fiddling with iPhones. In fact, she's terrific fun. Henry Holland should do her a T-shirt. Maybe for her hen night. Not that one of those is imminent, despite the rumours (she is said to be dating actor Alexander Skarsgard).
Speculation about her love life has been bubbling away ever since she split from Arctic Monkeys frontman Alex Turner five years ago. Understandably for someone who has been linked to every indie, pop and boyband member she has ever been in the same room with, she isn't hugely keen to talk about her love life. When I dutifully ask her the relationship question, she dutifully demurs from answering. "What am I meant to say to get out of this question?" she asks.
"Preferred not to discuss her personal life," offers her PR.
"What about if you just don't know?" she says finally. "Why does everyone presume that famous people know? What if you're seeing someone and you don't know how it's going to end up? I mean, there are so many variations. I'm in love with lots of different things. I do love love, though. I don't think love should make you feel uneasy. When you feel sick, I don't think that's love - that's infatuation. Someone who makes you feel like that is exciting - it's the one that you imagine when you think of an amazing affair - but that's not actually a stable love."
Stability must be the holy grail when you're hopping between London and New York, as Chung currently is. After nearly four years living in the East Village, she moved back to London in April, largely to work on her much-anticipated new clothing label, which has been mooted for years and is finally due to launch next May - though she's not meant to be discussing that yet.
"It's a full-time job," she says of The Thing She Can't Talk About. "It's hard not to talk about something that's so exciting, and also such a large portion of my life."
What with last month's launch of her second and final Archive By Alexa collection for M&S, her collaborations with AG Jeans, her art direction of the latest Ugg campaign, her fashion app Villoid (which allows you to follow your favourite brands and buy them) and her duties as the face of Longchamp, even the most accommodating of boyfriends might be forgiven for wishing she could spend more time on the sofa with him eating crisps.
Of all her projects, her three-and-a-half year Longchamp relationship is the most enduring. "I don't know why they continue to use me, but it's been nice to have worked alongside a brand for that amount of time," she says. Alexa recounts being on a recent shoot for them, and the weather being grim, and extra lights being brought in to counter it. "Suddenly I was like, 'I bet they're wishing they had a sort of Christy Turlington-type'. The type of vibe that it was, I felt ill-equipped to pull off. I was doing an impression of a Nineties supermodel to try and get in the zone. I had to do it in character; pretend to be really sexy for once. In order to pull it off, I had to look like I was seducing the camera."
"And you apologised before you did it," adds her PR.
"So English!" Chung grimaces. "I said, 'I'm going to take on the character of someone who's really confident and thinks they're gorgeous'. And they're like, 'Okay, off you go'."
But you are gorgeous, I want to say. But she is off again. "I went and got acupuncture in NY and the woman who was doing it was like (she affects an American drawl), 'How arrrrrre you?' and I was like, 'I'm a little bit stressed at work'. And she was like: 'You know what you need to do? Ask what would Brigitte Bardot do.' And I said, 'I don't know what Brigitte Bardot would do, probably talk about animals for a bit?' And the acupuncturist said: 'She would be sexy and juicy and slow, and she would get other people to do s**t for her. She wouldn't be the one busying around. You don't have to act like a man. Be more of a woman. Wear a dress all week and be juicy.'"
I tell Chung that I hate her acupuncturist, and that 'juicy' is a horrible word. She looks crestfallen.
"I thought it was an interesting... Oh s**t, now you've made me think of it completely differently," she says. "Do you want me to go back and tell her off?"
We then have a discussion about Brigitte Bardot that must remain off-record. "So here's what happens when I get interviewed," she says, after. "It will all be fine, and then I'll think, 'I don't want to be really boring because then it's dull for everyone, and I hate reading interviews where people are dull'. Equally though, if you're too relaxed, then you spend the next month before it comes out pranging out about things you've said."
It's at this point that it dawns on me that Chung is a people-pleaser. She might make a living from being stylish and on point, but she still suffers from the same insecurities as the rest of us. She doesn't feel sexy, she worries about putting her foot in it and she still feels like a fraud. "Oh yeah, absolutely, 100%," she confirms. "But I think everyone's like that - feeling a bit out of their depth."
Where does she get her sense of humour from? Her parents? "Yeah. Phil and Gill (Chung) are funny. They do like a good time. Sometimes I get cross with them because if I'm at work, for example at M&S or something, I like to have an air of authority around what I'm doing, and then my family roll in and just ruin it for me. They'll be, like, puking on the dancefloor or being carried out the back.
"Not that it was my parents puking," she adds. "It was another family member."