"I used to resent being called `demure' and `petite'," she says. "I never was the demure woman people imagined. I guess I am petite, but what can I do about that? Go on a rack? I can't say I feel passionate about it now. I don't go around doing surveys of public opinion about me. Perhaps I should go down to Notting Hill and hand out forms: `Could you fill this out? What do you think of me?' " (This sort of behaviour would be particularly unlikely just now, as she is adopting an abnormally low profile after reports of her split from Kenneth Branagh, her partner of five years.)
"The typecasting damage has already been done. When there's a headline about me, it's always something to do with corsets or English roses. You're stuck with a label, but it doesn't mean that much."
Indeed, this facile categorising can even have a beneficial effect. "Pigeonholes are good," she continues, "because I don't have to do much to surprise people. It's such a strict image that it's easy to break out of. All I have to do is wear modern dress."
In her latest venture Bonham Carter has, however, done much more than that to escape the corseted stereotype. For The Theory of Flight, she is not only in modern dress, but also in a wheelchair. In Paul Greengrass's challenging film she plays Jane, a defiant and darkly amusing woman with motor neurone disease who tries to persuade her wastrel carer, Richard (played by Branagh), to help her lose her virginity.
With her body twisted, her voice distorted and her trademark Pre-Raphaelite locks shorn, Jane is light years away from the floaty beauties Bonham Carter played in, say, Room with a View and Howards End. She is given to in-your-face pronouncements, and wears a T-shirt proclaiming: "I didn't get this far on looks alone."
This pitch-black sense of humour spares The Theory of Flight from the curse of worthiness. "I hope it isn't worthy," Bonham Carter reflects. "The film is not primarily about motor neurone disease. It's a love story."
And a feisty one, at that. "I didn't want to sanctify Jane. At first, she's a tough, unattractive character. But I liked the fact that she is not prepared to be upstaged by her illness. That's why she wears clothes like that T-shirt - which speak for her, as her voice is going. She wants to be seen as an individual. People should perceive that there's a person beyond the wheelchair."
Bonham Carter had an advantage in preparing for the role; her father has been in a wheelchair for the last 20 years. "That helped, because I didn't have to do so much research. Of course, it's a bonus I wish I hadn't had in the first place, but I do know a hell of a lot about what it's like to live with a disabled person and the impact it has on a family. If you live with disability, it's demystified. My dad is tremendously proud of the film. And he reverberates in it."
Inevitably, there was a debate about whether a genuinely disabled person should have played the role of Jane. "At first, I did feel queasy about making entertainment out of illness," Bonham Carter concedes. "I thought I could only be a travesty in the role. The producers did look at the possibility of a disabled actor, but it quickly became untenable because of the hours involved. The Motor Neurone Disease Association seconded that opinion and are completely in favour of the film. They had several representatives on the set all the time, and hope it raises the profile of the illness."
Despite the success of such films as My Left Foot and Rain Man, disability in the movies is still hard to market. The Theory of Flight did not set the box office alight when it was released in the US at the end of last year. "Apart from those who travel on British Airways, not many people saw it," Bonham Carter sighs. "A wheelchair and terminal illness are a major turn-off. It was not a great Christmas release..."
However, she had to raise her eyebrows at the US marketing campaign. "The poster was just two head shots. I looked at it and said, `Where's the wheelchair?'"
Dressed in a purple halter-neck top and black jeans - not a bonnet or a bustle in sight - Bonham Carter overturns many preconceptions. For instance, and this may come as a surprise in such a narcissistic business, she doesn't take herself too seriously. "A lot of the time when you're filming, you think, `How absurd, who are we trying to kid?' The whole thing is total artifice."
She feels less able to be flippant about her treatment by the press; Bonham Carter bears the scars of many a journalistic savaging. She jokes sarcastically that she and the press have such a good relationship that "we'll have several children together. The problem is that, to your face, journalists are often people you think you can trust. Then, lo and behold, you read their articles and think, `what an idiot I was. Come on, develop a bit of misanthropy'. You'd think I'd have learnt that by now.
"I'm not immune. You do implode with anger and get hurt. The thing is, actors are in the business of being vulnerable. We're the last people the media should be let loose on. We're super-sensitive, and yet the Rottweilers are unleashed on us."
Bonham Carter is likely to upset expectations again in her next film, The Fight Club. In David Fincher's (Se7en) controversial contemporary picture about two friends who have to prove themselves through bare-knuckle fighting, she plays the girlfriend of both Brad Pitt and Edward Norton. ("I lucked out there," she smiles.) After a screening at the Venice Film Festival last week, one critic commented that Bonham Carter makes "her biggest leap yet away from her familiar roles in period costume dramas."
Nevertheless, she won't entirely rule out a return to breath-constricting garments. "I'll get into a corset again if the writing is good," she admits. "There is such a paucity of good writing. You go for quality; it doesn't matter where or when it's set."
In the meantime, more character roles - such as a Scottish mother in Women Talking Dirty - are in the offing. "Perhaps it's because the looks have gone," laughs the 32-year-old. "I've always felt happier doing character parts, but in the past with my long hair I didn't look like a character actress. Now that I'm ageing, perhaps I'll get more.
"The funny thing is that all the character actresses want to play romantic leads. The grass is always greener - although up close, of course, it's often yellow."
But one thing we are unlikely to see is Bonham Carter in a genre action film. "You read them and think, `there's not a shred of character or psychology there'. There's nothing for the woman to do - apart from turn up and look decorative."
The days of doing that, she trusts, are long gone.
`The Theory of Flight' opens on FridayReuse content