LOTS of actors have wonderful smiles, but Anne Hathaway's was arguably a star before she was. In the Princess Diaries movies, a single flash of her beam could nervously apologise one minute, awkwardly charm and seduce the next.
That is no mean talent. Think of Doris Day or Julia Roberts. The ability to convey joy, to offer a simulacrum of happiness, is Hollywood currency, part of the reason that Hathaway has been working steadily and with increasing impact ever since she first took on that role when she was 18. But that was then. "I was a zygote," she says, recalling her entrance into the big leagues.
In Rachel Getting Married, Hathaway's first turn as the kind of movie star a film is built around, the only time you see her teeth is when her character, Kym, bares them just before sinking them into her sister or father or some other bystander.
The drug-addled woman who threatens to tear apart her sister's wedding by her mere presence, her character is a dynamo of narcissism, an ambulatory wound who smokes as if her life depended on it. Her character has sex in the basement with the best man, makes a skin-crawling speech at the rehearsal dinner and gets a shiner from a fight with her mother.
There has always been a lot more to Hathaway than the grin, which is on ready and easy display as she sits down to discuss a Big Role in an Important Movie.
She has changed lanes in her career with Rachel Getting Married. She is among those tipped for best actress in this year's Oscars, where she is likely to join Meryl Streep – whom she idolises after working with her in The Devil Wears Prada – and Kate Winslet, whose work causes Hathaway, a very assured speaker, to tumble into hyperbole.
When an actor has made a very visible appearance at a young age, there is a temptation to say that the audience has watched her grow up in front of their very eyes. In Hathaway's case it's not a totally misguided impulse. As she made her way through two Princess movies, Nicholas Nickleby, Ella Enchanted, Brokeback Mountain, The Devil Wears Prada, Becoming Jane and Get Smart, you could see her improving as an actor. But Rachel Getting Married is not the next incremental step on her acting journey – it's something else completely. And from the start she had to have the role.
"We were sitting around the table with different people reading, like a year before the movie was made, and Anne had her part memorised," says Tom Bernard, the co-president of distributor Sony Pictures Classics.
Hathaway says she was drawn to the challenge of playing a barely recovering addict who copes by making the world pivot around her misery.
"I wanted the part because I thought, 'What would it be like to have a manipulative streak a mile wide you're completely unaware of?'" she says, nursing a coffee. "Yes, she is narcissistic, downright selfish in fact, but she is actually being the best version of herself she can in every situation, and it's not for me to judge her for it."
Jonathan Demme, the director of Rachel Getting Married, decided he needed Hathaway to make the movie: "She was my motor for this movie. She has this rounded, empathetic connection with people that made this a real shared exercise. It's her movie, but she never acted that way on the set."
Jenny Lumet, who wrote Rachel Getting Married, says she wondered how Hathaway would get her arms around a role that required her to use words as both shield and sword.
"This role required somebody who has a facility with language – these are women who talk in a certain way, who talk very fast – and as soon as I heard her read, I knew she would be amazing," Lumet says. "She has great big eyes, like teacups, and a huge grin, both of which make her seem really intellectually hungry."
But the fast mouth doesn't fully explain her ability to convey such a conflicted, tortured young woman. A trick of craft? Probably, but keep in mind that the sunny, goofy girl audiences had previously seen in the movies really only existed in those movies. Her career has not been mirrored by the same kind of personal equilibrium. Her one-time live-in boyfriend, Raffaello Follieri, was arrested and convicted on fraud and money-laundering charges in the past year, and her personal journal, along with jewellery he had given her, became part of the case. She won't talk directly about it today, but goes there in her own fashion.
"I've not made perfect choices by any stretch of the imagination, but I think by and large I've managed to avoid making foolish decisions," she says. "I've never lost custody of myself. I know who I am."
We talk about Lindsay Lohan, another promising actress, who ended up on the other side of that line. "The thing about sweet Lindsay, I just think she's had to grow up very publicly, and she's grown up in a way that a lot of girls I know who don't have to deal with the spotlight have grown up. Which is to say, imperfectly, maybe a little messy at times."
In conversation Hathaway seems more comfortable talking about growing up in New Jersey and staring at the lights of the city than about becoming one of the glittering people that others make a fuss over.
"My goal in life is maybe I could make it on to Broadway and, if I found the right role in the right year, maybe get nominated for a Tony," says Hathaway, who is also an accomplished singer.
"That was the extent of my dreams, and the fact I have people championing my work is not really something I expected, to be perfectly honest. I didn't think I was that kind of an actress."
There was a time when she didn't think she was an actress at all. Then Ang Lee cast her in Brokeback Mountain, to play the wife of Jake Gyllenhaal's closeted cowboy, Jack Twist.
"I had just about given up on myself as an actress when it came along," she says. "I just didn't think I was any good, and felt lost. I didn't know how to communicate with people.
"And then to be cast as a character who had nothing to do with who I was, and do it in the company of people like Heath Ledger and Michelle Williams and not stick out like a sore thumb, was huge."
When it was screened at the Venice Film Festival for the first time, she ran out of the cinema before her first scene.
"The movie was so beautiful, so perfect, I thought I would ruin it, so I left. I came back just in time to see a scene where my breasts were on screen, so that was special," she says with a smile.
Successful actors can reflect modesty when it becomes them, but Hathaway appears to come by hers honestly. People love working with her because she is a big deal but doesn't act like it.
"I think she has this availability, this immediacy, that is not behind any kind of carapace or artifice," Streep says. "I'm not surprised to see her going deeper and doing more vivid work. People develop this expectation of who an actor is based on the roles they have had, and I find that so reductive. She is the kind of actor who can do all sorts of things."
Hathaway can be seen from this weekend in Bride Wars, a comedy co-starring Kate Hudson, and has a turn as the White Queen in Tim Burton's Alice in Wonderland. But for the next month at least she will be among the mentioned, having fought for and performed a role people are still talking about, still rooting for, in the Oscar race.
"It would be extraordinary, obviously, to be mentioned in the same breath with my hero, Meryl, and Kate Winslet," she says. "But if that happens, I know my place. It's not their first time to the rodeo, so there's a humility that goes along with that that I'm very aware of."
• Bride Wars is released on 9 January. Rachel Getting Married follows on 23 January.
FACT BOX: OSCAR'S LEADING LADIES
Anne Hathaway's role in Rachel Getting Married has been tipped to win her a best actress Oscar, but who is the competition?
Streep, left, could be nominated for her performance as a vengeful nun in Doubt, perhaps helped along by the goodwill created by her turn in Mamma Mia!.
Winslet is good in both The Reader and Revolutionary Road, and is arguably due an Oscar, having been nominated five times before but never won.
The star of Happy-Go-Lucky could be this year's Brenda Blethyn, Marianne-Jean Baptiste or Imelda Staunton, all of whom won plaudits for roles in Mike Leigh films.
Could also be a contender for her role as a grieving, then angry mother in Clint Eastwood's Changeling.