Beauty, talent and an Oscar nomination aren't enough, it would seem, to stop Britain's brightest young female actor from worrying about whether her bum looks big in a new dress. Within minutes of talking to Carey Mulligan, it is obvious that the 24-year-old Londoner is no more immune from the anxieties of growing up than the rest of us. And though she can call on Prada to help hide her "problem area", this engaging self-doubt is undoubtedly part of the reason why Mulligan retains buckets of modesty and enthusiasm despite burgeoning adoration from the Hollywood glitterati.
It's not that she comes across all girl-next-door: she's a bit more north London twenty-something than that. You can imagine her being talked into karaoke in a trendy bar after a few drinks with her friends. She swears quite a lot, to make her point rather than for effect. And, against all expectation, she seems genuinely excited to be talking to yet another journalist. This gusto despite a year of non-stop film festival appearances to promote An Education, a string of British and international industry accolades under her belt and a well-publicised blossoming relationship with the Transformers star Shia LaBeouf.
Plainly she has not, yet, been swallowed up by the Hollywood PR machine and so chats candidly about what had been a truly remarkable year. Not since Helen Mirren has a British actress been received so well on the fickle world stage. And it is entirely possible that she will walk away with two Baftas next Sunday.
"All of the awards things have been a huge, huge surprise. None of us expected this sort of stuff when we made the film. The Orange Rising Star* was amazing because it's like being invited in. It's like saying hello to the world, really, with a bunch of amazing actors. While the Oscar feels like a ... well, it hasn't really sunk in yet. When you dream about being an actress when you're six years old, you dream about having light bulbs around your mirror. It's that kind of fantasy, the fairy-tale version of what it is to be an actor, so it's mad that it is coming true. When I saw my nomination I just remember thinking, I hate that picture, and then going kind of numb. It took a lot of sinking in; it still hasn't."
Though she has won critical acclaim for practically every on-screen and theatre performance since her debut as Kitty Bennet in Pride & Prejudice in 2005, it was her role as a middle-class 16-year-old schoolgirl, Jenny Mellor, which propelled her, and An Education, on to the global stage.
In the film, based on the memoirs of the journalist Lynn Barber, Mulligan plays a spirited suburban teenager who forgoes her dream of Oxford University for an older man with sophisticated friends and sophisticated evenings in 1961 London. Her assured and luminous performance lifts Nick Hornby's screenplay to heights that it might not otherwise have reached.
"Lynn Barber said that she believed herself to be an existentialist at that time, which I thought was hysterical. But it made sense of her pretentiousness and made her easier to play, because it helped me to understand why she got swept up in it.
"I didn't have a proper boyfriend until I was 19. I was a bit of a geek, a bit like a tomboy growing up with my brother and his friends, so I was nervous about all that stuff, and much more cautious than she was. I'm much more romantic now and more easily swept away than I was when I was 16."
Plainly she has not yet learned that volunteering information about her past private life is an invitation into its present. So was she swept off her feet by Shia then? "I led myself into that one," she laughs. "I will say that our characters are very much swept off our feet in Wall Street. How about that for a diplomatic answer?"
In between filming Wall Street: Money Never Sleeps – Oliver Stone's sequel to his 1987 classic – Mulligan has done more than her fair share of promotional work for An Education since it won two awards, and a distribution deal, at the prestigious Sundance Festival last January.
Her edgy dresses and new impishly short hair cut – which she hates – have become familiar on the red carpet in recent months, and she has a growing number of starry anecdotes to share. Quentin Tarantino, whom she is desperate to work with, spent 10 minutes at the Golden Globes telling her how he loved her expression during one scene. So he's a fan too? "He's only a fan of one moment in that film, that's all. He's amazing." Her enthusiasm is sweet, anything but boastful.
From Berlin via Toronto to Melbourne, she worked the festival circuit like a pro last year, yet the novelty has not worn off. Neither have the uncertainty and shyness which means Mulligan, perhaps unlike some of her contemporaries, finds it easy to keep both feet on the ground. While her strong performances and her looks have led to widespread comparisons with Audrey Hepburn – also nominated for her first Oscar at the age of 24, for the 1953 film Roman Holiday – Mulligan has dismissed this as like comparing Shrek to Hepburn.
And widespread adoration has not eased her own doubts about what she sees in the mirror, nor has it alleviated red-carpet nerves. "I don't like wearing tight things and I'm really self-conscious about things that are too short. I've never felt comfortable wearing revealing clothes. Doing red-carpet stuff is intimidating enough, so I'm wearing a lot of Prada as the clothes are a perfect shape for me, because I'm bottom-heavy. Or else I like wearing unconventional things because then it feels like you're putting on a costume."
Her hair fuels more self-doubt. Cut short after it was left "fried" from peroxide – she turned blond for Michael Mann's Public Enemies although most of her scenes ended up on the cutting-room floor – she is desperate for it to stop looking "like a mullet" and grow back.
Born in central London, Mulligan comes from a family with no previous acting connections. When she was three, her father took the job of managing the European arm of Intercontinental Hotels, which meant she went to primary school in Düsseldorf, Germany.
She was at her secondary school, Woldingham in Surrey, when she met the actor, novelist and screenwriter Julian Fellowes, who had come to give a talk as a favour to the headmistress. She'd already been turned down by drama schools including Rada and Central School of Speech and Drama, but her enthusiasm and persistence – she wrote to Fellowes afterwards asking to meet him again – convinced him to help her, and several phone calls later she had an audition for Pride & Prejudice.
Her father has now retired, but her mother still teaches hotel management and catering two days a week. Her elder brother is a civil servant at the Ministry of Defence. She is taking all three to the Oscars next month.
"I was sort of unabashedly enthusiastic. It wasn't like I wasn't taking 'no' for an answer, more like I don't know what else I would do with my life if I don't get to do this. And people just responded to that enthusiasm and were really generous. From Julian Fellowes onwards, people have given me way more time than has been required."
Now she is on the cover of Vanity Fair as part of the magazine's much coveted Hollywood issue. It was the third time in a month she'd been photographed by Annie Leibovitz. She looks, it has to be said, a little awkward.
"It was a good day of trying on clothes that were too small for me and trying to sit in a flattering way. I'm not that great at having my photo taken, so I often look like I don't want to be there. Annie makes you feel comfortable after a while but it's still staring down the barrel of a camera, which still feels pretty unnatural."
Despite months in LA, hanging out with the great and the good, Mulligan hopes, somewhat naively, that all the hoopla will dissipate after the Oscars next month so she can then go skiing in Austria, grow her hair back without being photographed and basically get back to normality. It seems unlikely.
Frankly, with ambitions to get back to the Royal Court and work with the directors Michel Gondry and Darren Aronofsky, her chances of hanging out in her local pub seem diminishingly slim.
She is philosophical. "No one expected any of this to happen for An Education, so it's been a completely crazy ride. It's a sort of once-in-a-lifetime thing, so I'm writing stuff down and trying to remember it. As surreal as it is and as much of an honour as it is to be with people you admire so much, well, I'm just going to enjoy it. After that I can't wait to get back to work.
"I get the same feeling that I got when I got Pride & Prejudice, every time I get a part that I really want. When you've read something that you really love and you're waiting to hear, nothing, not even awards stuff, beats that feeling. When you know it's your gig, that's the best feeling in the world."
1985 Born in Westminster, the younger of two children. Moves to Germany at the age of three. She and her brother Owain attend an international primary school in Düsseldorf.
1996-2003 Attends the all-girls' private school, Woldingham School, in Surrey. Is turned down by three top drama schools.
2005 Makes her film debut as Kitty Bennet in Pride & Prejudice.
2005 First TV role as Ada Clare in the BBC's series Bleak House.
2008 Plays the role of Nina in Chekhov's The Seagull on Broadway to critical acclaim. Loses out to Angela Lansbury in the Drama Desk Awards.
2008 Wins Best Actress at the British Independent Film Awards and Breakthrough Performance at the Hollywood Film Festival.
2009 Lead role in An Education as 16-year-old Jenny Mellor.
2009 Meets her new boyfriend, Shia LaBeouf, while filming Wall Street: Money Never Sleeps, the sequel to Oliver Stone's 1987 Wall Street.
2010 Nominated for Best Actress for her part in An Education at the Oscars, Golden Globes and Baftas.
2010 Shortlisted for the Orange Rising Star award – the only people's award at the Baftas.
2010 Two films set for release: Wall Street: Money Never Sleeps and Never Let Me Go.
Carey Mulligan is nominated for the Orange Rising Star Award at the Orange British Academy Film Awards. To vote go to orange.co.uk/bafta. An Education is out on DVD on 8 March