"READING things about myself that aren't true drives me crazy!" Kate Upton mock squeals as we discuss the American tabloids' obsession with her love life. "I've managed to block it out, but my family really hasn't - so they'll read about me and then call me up saying, 'Are you alright? I saw this happened' and my mum will call and say: 'Well, I saw you went to Vegas, when you could have come to the family reunion…' and I'm like, 'mum, I swear, I'm in Europe!' It's insane!"
Drinking a purifying-looking green drink with her feet curled up beneath her, she could be any 22-year-old - except for the face, and the hair, and the body, and the Cameron Diaz film she just starred in, and the multi-million-dollar Bobbi Brown contract, and the Vogue covers... and yet still, somehow, the girl-next-door tag still seems feasible.
Upton promises she's jetlagged, but is still bright-eyed and bushy-tailed to an almost unbelievable, and certainly unachievable, degree. A cheerleader for confidence, she really practices what she preaches - talking animatedly on a range of topics and punctuating each anecdote with plenty of nodding and laughing and kindly sympathising.
She's a girls' girl at heart, that much is clear, but there's no denying that the exterior is decidedly boy-friendly. Her pneumatic figure, often accentuated by her on-duty attire to almost cartoonish proportions, is nothing compared to her Disney-worthy face, with peachy skin and huge oval eyes that any Princess would be proud of. Men attend to things in the room as we talk - checking clipboards and water levels with an attentiveness that one suspects is reserved for Upton wherever she goes. If the Queen must believe that the world always smells of fresh paint, then Upton surely must assume that all men are perennially smiling and helpful to a fault. Except, perhaps, the paparazzi with whom - like most actresses and models - she has a complicated relationship. But even they don't awaken any meanness.
"I enjoy the red carpet for the first 10 minutes and then I'm like, 'Alright….let's go,'" she smiled. "Sometimes the photographers get really bossy, like 'blow a kiss!', 'smile!' and I think, 'You don't know Mr, you're not a model! This outfit is meant to be fierce, it doesn't go with smiling!' When I first did red carpets, I used to listen and do what they said - but now I don't."
In London for her role as a Gillette ambassador, she has been enlisted to talk about men's grooming - helping shy, unkempt men take control of their image to create something altogether more dashing.
"Being groomed is about confidence, and I'm always talking about women's confidence but men's confidence is important too," she said. "I don't really have a dealbreaker in grooming, because I think if a man is confident and walks into the room that way, I just fall for it. Tom Ford is the perfect example of great grooming."
Upton loves lots of things about her job - learning new things, meeting people, travelling - she's a glass-half-full sort of person. A self-appointed poster girl for confidence and contentment, she's the ideal brand ambassador - melding eye-watering good looks with a down-to-earth charm, but fashion purists complain that supermodels, by their very definition, should be unattainable. Upton is nonplussed.
"My mother always taught me that smiling when you walk into a room is the best beauty secret, so if I'm nervous when I walk in I just smile, and I think everyone warms to you quicker that way," she nods. "Sometimes people look stern when I come on set, just because they're concentrating or getting ready for their day, but I'll chat and smile and finally I break them down!"
Despite her wide-eyed looks and Labradoric enthusiasm, Upton also seems somehow older than her years - and not just because of her very grown-up figure. She's what Americans might call "centred," but what we Brits would probably call "normal" - pretty, polite and generally satisfied with her lot. My stiff-upper-lip-style handshake is shamed into submission by an unexpected hug and a warm genuine thanks for "coming to see me". See, she's not a supermodel, she's just like us.
Kate Upton is the ambassador for the Gillette men's grooming campaign.