Pattinson, who turns 23 later this month, has become an international pin-up since Twilight was released last year. He's probably bigger news even than Daniel Radcliffe. After all, Harry Potter still seems like a little boy while Edward is a passionate, redblooded teen vampire in love with a mortal schoolgirl called Bella. Forget that gargoyle nonsense, too: Pattinson is an unlikely fusion of Johnny Depp and Doctor Whoelect Matt Smith. He favours the same vintage clothes as Depp and the actors share the same tough femininity; he's got the same architectural hair as Smith, the same asymmetrical features and strangely alluring face. Oh, and he's six-foot tall with the lean body of youth.
Yet Pattinson himself can take none of the attention seriously. Educated at a private day school in London, he has the kind of posh English accent Americans love, but he's not remotely pretentious or full of himself. His Twilight co-star Kristen Stewart, who plays Bella, once said that Pattinson can't lie; he also can't seem to stop talking. Right now he's describing the hotel room in Vancouver, where he's been filming New Moon, the second in the Twilight quartet. "I've been living in this windowless room on the 30-something floor. Because the people who built it were afraid of people killing themselves! It's one of those business hotels. I guess they're worried about not being able to charge so much for rooms if guests were killing themselves …"
Most actors live in apartments, or at least hotel suites, while on set. But not Pattinson: "I've settled there now. It would take about three weeks for me to gather all my belongings. I don't let the maids in. I don't even pull the duvet down now because I don't want to see what's underneath."
There are always fans waiting outside the hotel but he tries not to think about the phenomenal level of fame he's reached in north America; he says he'd go mad if he did. So he tries to disguise himself: "But instead I'm just getting more and more conspicuous; I'm wearing two hoods, a hat and sunglasses, which kind of stands out in the middle of the night. So I'm learning to sprint."
At times Pattinson sounds grown-up, but he also lapses into adolescent silliness. Ask if he has a fake hotel name and the giggling starts: "I was Clive Handjob in Paris. Everyone in the hotel called me 'Monsieur Handjob'. That was good, cheap fun."
When he got the role of Edward, Pattinson was sent to have his hair cut and dyed. He was given a personal trainer and, for the first time, got himself a six pack. He was also sent for media training to help him handle the juggernaut of publicity required for Twilight (in the US principal cast members have to participate in events such as "hype-building panels" to push the fi lm). He may now look more like a movie star but he still says things he shouldn't. In one interview, he volunteered the information about the Valium and then seemed to dismiss Little Ashes, an arthouse film he made before Twilight, as "nothing". He also pointed out, rather brashly, that "we didn't even have trailers".
Pattinson's experience of film-making is limited – at 17, he won the small part of Cedric Diggory in Harry Potter And The Goblet Of Fire, a role he reprised in the Order Of The Phoenix; he then lived off the pay cheque for a few years – but he's already got regrets. Little Ashes explores the homosexual relationship between surrealist artist Salvador Dalí and the romantic poet and dramatist Federico García Lorca in Spain in the early-1920s. It's a fascinating period – the surrealist film-maker Luis Buñuel was also hanging around – but art historians have already questioned the veracity of Philippa Goslett's script, saying that there's no proof Dalí and Lorca actually consummated their relationship.
Made for a modest £1.4m, Little Ashes suffers from its ambition, and Pattinson – with only Harry Potter under his belt – struggles to portray the hugely complex Dalí with any real conviction. Yet he briefly blows up when I mention his dismissal of the film as "nothing". "I hate having to do all this shit! I've already been told to apologise for saying it. I was just trying to say that it was a tiny, little film. It had a minuscule budget. I was just trying to say that if Twilight hadn't come along, I don't know how much Little Ashes would have been publicised. In an ideal world, everyone would go around watching arthouse films about Dalí and Lorca. But a lot of people have no idea who Lorca even was."
He collects himself: "People love all the negative stuff – 'He doesn't like the film!' 'He's a homophobe!' Oh great." Now that he's been told to make amends, Pattinson is actually taking Little Ashes more seriously. He even watched it the other night. And he never watches himself on screen, ever. "It's like self-flagellation, so why would I bother? And I didn't want to piss on anyone's grave. It was hard to watch my first scene, in which I turn up in this funny little hat … I was worried about watching them, but Dalí and Lorca's sex scenes were in fact the best scenes."
Twilight fans, being obsessive, will certainly be checking out a nearly-naked Pattinson in Little Ashes (be warned: this is pre-six pack, though his skin is vampishly livid). That's the problem with suddenly becoming very famous; the skeletons fly out of the closet at breakneck speed. And Dalí's fetching little hat in Little Ashes is nothing compared to the succession of dodgy old adverts that have reappeared recently. There are some particularly fetching ones on the net of Pattinson in pants or trunks, with bouffant hair and a cheesy smile. "Really? When I looked like a real … weirdo? I swear to god that's illegal! It's just so embarrassing. Actually, I saw one the other day."
Pattinson does seem to be overwhelmed with his lot right now. He hasn't asked Daniel Radcliffe for advice – "I haven't got his number!" – and is predictably prickly when asked about being defined by his role in Twilight. He spouts a lot of media training rubbish about making absolutely the best movie he can in the hope that people will see him as a good actor and not just as Edward. In the brief time I talk to him, it seems that he's in a place he never intended to be; after all, he was contemplating giving acting up before the Edward audition.
But perhaps he's happy with his life and it's just the interviews he hates. He says that when he's doing phone interviews in his hotel room, he sometimes wishes there was a window to jump out of. He's only joking, of course, but it seems that the actual process of acting has got lost in the fog of Hollywood publicity. Sometimes he has fun making things up in interviews. Such as? "I do really intellectually highbrow stuff in my downtime. I read first-edition Shakespeare. I write poetry. I'm trying to get my masters in neuroscience. That's the kind of guy I am." He pauses, clearly amusing himself: "Man, I don't even know what a masters is." And he laughs hysterically as he creates another shape with his hair.
• Little Ashes is out on Friday