Robert Pattinson. Twilight. Getting naked in indie movies. Fame. These are some of the things we won't be talking about with Kristen Stewart. "Oh, good." says the actress, slightly taken aback when we give her the good news. We're sat on the roof terrace of a hotel - heavily populated on the ground floor by security guards - and it's week two of Cannes Film Festival. Only 22-years-old, Stewart is being afforded the kind of elite protection from the media usually reserved for Hollywood's biggest megastars. But we don't really want to ask her about that either.

In fact, LW Lies only has one question: what does Kristen Stewart want to talk about? "Right," she says. Then she thinks. "I don't want to sell myself. People are so weird. They suddenly find themselves so interesting that they think they're worth selling. Typically speaking, the most interesting thing to me about myself is, right now, the fact that On the Road is coming out. And I want to talk about On the Road.

To talk about on the road is to discover that, although people ask Kristen Stewart a lot of questions, the answers all lead to one place. It's really simple: she's a 22-year-old kids who's crazy-stupid in love with her job. "Oh my god, I fucking love it so much," she beams. "I'm not Maryloul; I'm Sal. Right now, I feel so full. I'm like, bursting. I should be working. I don't want to take a break. It's funny, on set, I don't have to go to the bathroom, I don't have anything wrong, I'm perfectly fine, so through-and-through. I'm not hungry. I'm literally not even in my own body. They wrap and they send me back to my trailer and I fucking fall to pieces. I suddenly realise that I've had to pee for six hours. And I'm starving."

This kamikaze work ethic left her co-star Chris Hemsworth dumbfounded on the blockbuster Snow White and the Huntsman. Why, wondered the Aussie heartthrob, was she attacking a basic Hollywood fantasy like it was a Paul Thomas Anderson drama? "Awww..." she smiles, affectionately. "He's the same way. Well, he takes it very much at face value. Sometimes I need to make myself do that. I just really am trying, trying, all the time. I mean, Walter actually said to me several times during On the Road, 'Stop reaching, you're already there.' But I like to be scared. I love to suddenly feel out of control. Actors walk around wearing these little tool-belts of acting skills. And I just don't find that interesting to watch. I never want to see someone who clearly can cry at the drop of a hat. That's so uninteresting. And so many actresses are so fucking crazy. They're emotional wrecks, so they pretend to be these characters. But the emotions aren't coming from the right place. Do you know what I mean?" And you have to remind her: this is your interview: you tell us.