'To be honest, I can't really let it sink in that it's all over,' she sighs. 'It doesn't quite feel real.'

We're sitting in a luxurious room on opposite sofas, Watson wearing navy jeans, a cream knitted jumper and sleek black boots, matching the dark nail polish on her fingers. It's understated but classy - very Emma Watson. After she politely removes a giant glass bowl of white roses on the table between us, I get a proper glimpse of Watson's new haircut that she's just unveiled on her Facebook page. Gone are those long brown tresses, replaced by an elfin crop reminiscent of Mia Farrow's in Rosemary's Baby. All of a sudden, she no longer looks like the gawky teen of Potter-world. 'People say I do look different,' she says, beaming, relief in her voice.

She had been desperate to cut her hair since she was 16, but her Potter contract wouldn't allow it. Likewise, she wasn't allowed to tan or do any so-called dangerous sport - from skiing to white-water rafting. 'Sometimes, as a child, I felt like I was wrapped in cotton wool a little bit,' she sighs.

If teenage years are a time for experimentation and rebellion, Watson was legally bound not to. Rather, she had to develop remarkable powers of self-discipline for one so young. 'It's made me a stronger person than I ever could imagine I would be,' she says. 'I feel as though, after having done this, I could do anything, really. In terms of acting, in terms of life in general, it's really made me who I am.'

Indeed, how many 20-year-olds can say they've already modelled for Burberry, designed a clothing line for ethical label People Tree, and been spotted in the front row of Chanel catwalk shows - not to mention got an estimated GBP20 million (HK$244 million) in the bank? But Watson knows it's come at a price. The idea of a 'normal' childhood was impossible, she says.

'It consumed my entire existence. It really did. Trying to have a life beyond Harry Potter was such a struggle. Trying to have time to take exams or go to school or see my friends, or be anything other than Hermione, was a real battle.'

Unlike Radcliffe or Grint, who both left school early, Watson carried on with her studies - cramming for her A-levels around the shooting of sixth instalment Harry Potter and the Half-Blood Prince. She's now on her first year at the prestigious Brown University, in Rhode Island, studying for a liberal arts degree. 'It's like being a kid in a candy store,' she enthuses, referring to the multiple subjects she can take. But there are other things, such as late starts. 'I confess, this semester I didn't take any classes before 10 o'clock. And I enjoyed every single minute of those lie-ins.'

Like any student leaving home, Watson is experiencing a newly found freedom. 'It's nice to have time to figure out who I am,' she says. 'I spent all of my life figuring out who this character is, and playing her and being her. I haven't had much time to be Emma. I wish I knew Emma as well as I knew Hermione!'

Arguably Watson knows the character almost as well as her creator, J.K. Rowling, author of the Harry Potter books. According to Deathly Hallows director David Yates, the young actress came up with the 'haunting' idea that sees evil witch Bellatrix write 'Mudblood' (a derogatory term in the Potter universe) on Hermione's arm.

With the final episode seeing Hermione, Harry and Ron go on the run as they seek out a means to bring down the evil Lord Voldemort (Ralph Fiennes), it's the darkest of the series since the third instalment, 2004's Harry Potter and the Prisoner of Azkaban. Much of the film sees the young wizards camping out in the woods, away from the safety of the Hogwarts school where the preceding films are all set.

'It's incredibly unusual. It's just the three of us holding the film. We haven't really been given a chance to do that,' Watson says. 'And we all loved having the space to really develop our characters and their relationship and for the story to be focused on us.'

If you're looking for symbolism, the final shot is of a stunt in which all three jump onto a crash mat - later replaced with a burning fireplace by computer wizardry. Talk about taking a leap into the unknown. 'I think the boys were slightly more in denial,' she says of their tearful last day. 'But I was trying desperately to make myself feel it. I wanted closure. I wanted to really feel like I'd completed. I was worried I'd walk away from the set and think 'Oh yeah, I'll be back again' and then it hit me a year later.

'I was like 'I need to really process that this is the last time I will be here' - so I'll be fully able to move on with my life.'

During her years in the Potter franchise, Watson rarely ventured outside of Hogwarts, only voicing a role for animated film The Tale of Despereaux and appearing in BBC drama Ballet Shoes, in which she plays an orphan who becomes an actress. Yet already, since completing Deathly Hallows, she's shot her first post-Potter part - a supporting role in My Week With Marilyn, in which she plays the wardrobe assistant to Marilyn Monroe (played by Michelle Williams) during the shooting of The Prince and the Showgirl. 'I can't believe no-one's made this film before,' she exclaims. 'She's such a fascinating creature, yet no-one has dared to try to tackle it.'

She admits it was a relief to play someone other than Hermione Granger. 'I didn't feel like her for a minute. I'm always worried when I take on a new role that I will just feel like her, but I didn't. So that's given me some confidence.'

In the past, Watson has referred to herself as like 'Bambi in the headlights' when she started acting due to her lack of experience. The daughter of two lawyers, Jacqueline Luesby and Chris Watson, she didn't come from an acting background and, much to her chagrin, never had any formal training (which may account for why she took a five-week summer course in Shakespeare at the Royal Academy of Dramatic Art a couple of years back).

Born in Paris and raised in France in her early years, when her parents divorced she moved to Oxfordshire with her mother and younger brother, Alex - which is where, as a nine-year-old, she tried out for the role of Hermione. If playing one character for a decade has offered her a 'stability' that's all too rare in the acting profession, she's convinced people assume that she's just the same as her character - a bossy little madam.

'People definitely think that they know me. They really associate me with that role and they've got me in quite a tidy little box.'

Does she find that annoying? 'I used to get really frustrated with it. And really worry about everyone seeing me just as Hermione,' she says. 'Now I've just let it wash over me. You just have to be patient and realise it takes time, and that people will see you in the end.'

Between studies at Brown and the Monroe film, Watson's already made great strides towards shedding the role that's brought her fame and fortune. Perhaps this is why she seems relaxed about life after Hermione.

'Everyone else seems much more worried about it than I am,' she says, looking me in the eye. 'I'm not really worried about it. Maybe I should be but I'm not.'

Harry Potter and the Deathly Hallows Part 1 opens on December 16