"It's like being compared to people who've been in massive movies who just sort of disappear afterwards, even though they probably had incredibly fulfilling and successful lives," he says, nibbling on a fingernail.
"Like Luke Skywalker." He scratches his head. "What the ****'s his name?"
Mark Hamill.
"Yes! People are like: 'Oh, the Mark Hamill curse'. And 'poor Mark Hamill'. Jesus Christ." He tilts back in the chair and laughs, apparently oblivious to the state of his T-shirt. "I mean, I'm sure he did fine."
It's easy to forget that this charming shambles of a man commands at least US$12 million [$15 million] a movie.
The cheekbones are a clue, but his eyes seem further apart than you expect - it's a model's face, more attractive in 2D. And Pattinson doesn't have any swagger or strut about him. As tall as he is, he doesn't impose. His body language is loose, approachable, self-effacing. He's not at the summit admiring the view so much as peering down and hoping he doesn't fall off.
"I think of impending doom all the time," he says with a shrug.
This apocalyptic fear stems from the way his career started. One minute he was a complete unknown. And then, out of a clear blue sky, Twilight happened, and he turned into Elvis. Girls on every continent went bananas, as did their mothers. In 2010 Time magazine declared Pattinson one of The World's Most Influential People. And now the end is nigh.
Breaking Dawn is the last book of the series, but Summit Entertainment, determined to milk the fans down to their last shrieking dollar, has pulled the Harry Potter trick and split it into two parts, with the second instalment out next year.
How they manage to get two movies out of the final book will be interesting to see. The plot of Breaking Dawn, in which the vampire-human romance between Edward (Pattinson) and Bella (Stewart) finally reaches the marriage altar, doesn't offer quite the all-out action climax of, say, Harry Potter and the Deathly Hallows.
"In career terms, Twilight was like a security blanket," Pattinson continues. Then he furrows his brow for a moment and corrects himself. "Not a blanket - a safety net. I had a three-or four-month window between each one during which I could do another job. But whatever I did I knew that I'd have another Twilight movie on the way, which is theoretically guaranteed to make a lot of money. So I could always afford to fail."
Now the net is gone. The stakes have been raised. He once described choosing roles as "crippling".
"After the last one comes out, you can kind of have two failures - and they'd better be low-budget failures. Because if you have one big-budget failure you're pretty much done in this environment."
It's an odd thing to say, given the circumstances. After all, he's the second-richest actor in Britain behind Daniel Radcliffe, with a fortune of some $64.4 million. He's an international sex symbol who need never work again.
If there's anyone who should not be nervous about the future, it's Pattinson. And yet he is.
"It's different for Kristen, for example," he continues, warming to his theme. "She doesn't think about it like that at all, because she grew up gradually, doing independent movies and stepping up the ladder, whereas I was doing progressively smaller movies in England, after Harry Potter ... to the point where I was doing nine-day shoots for, like, 20p and a packet of Space Invaders. And then this happened. So I'm not just another actor who's around and jobbing. When you hire me for a job, you're hiring ..." Twilight guy?
"Yeah. I'm now this 'thing' that's supposed to be something. And if you then don't fulfil that expectation, what the **** are you?"
It's a fair question. In some respects, he's just a nice middle-class boy from a vaguely bohemian household in Barnes, west London. His father imported vintage cars and his mother was a booker at a model agency. His two older sisters would dress him up as a doll and call him Claudia (Pattinson has always been subject to the madness of young girls). He started modelling at the age of 12, putting those cheekbones to use - shortly after he was expelled from school for being a bit of a truant. But Pattinson never thought of acting back then. His passion was music, and still is. Those scenes in Twilight where he's playing the piano are actually Pattinson's hands.
Then his father persuaded him to join the local amateur dramatic society. Pattinson had wanted to finish school and go to university to do a degree in international relations - he'd toyed with the idea of becoming a political speechwriter - until he landed the part of Cedric Diggory in Harry Potter and the Goblet of Fire.
It was a huge break in a global movie franchise, but even though he shone in the role, it didn't pave the way for better things: the parts he was offered afterwards were smaller; his career went into reverse. He had a rock band called Bad Girls, then started playing solo acoustic guitar gigs under the stage name Bobby Dupea.
When he did go to LA, to give Hollywood a shot, he spent his days playing music in bars or going to the movies. His agent, Stephanie Ritz, let him sleep on her couch. He felt bad that Ritz had represented him for three years but he'd never nailed an audition. Then the part of Edward Cullen came up. Director Catherine Hardwicke was having a hard time filling the role. She'd tried Orlando Bloom and Hayden Christiansen.
She'd auditioned 5000 boys for the part before Pattinson.
"The audition was at Catherine's house in Venice," he recalls of the moment that was to change his life, and his lifestyle, forever - which involved messing about on Catherine's bed with Kristen, to see if they had any chemistry.
"It was me, her and Kristen, and her assistant videotaping it. I was the last one of the day and I was in there for four hours, which was longer than anyone else before me. So I kind of knew. I was like: 'Hmmm, something's happened'. "And it was the first time I'd ever sent an email afterwards, as well. Like: 'I had a really great experience in the audition'. You know, kissing the director's arse. I always thought that was, like, the cheesiest, most pathetic thing to do. But it worked!"
He's said that he expected Twilight to be a "really serious" indie film - "I had no idea it was going to be this big thing you'd get on Burger King hats" - and as well as mass acclaim, it has, of course, had its critics. (As Stephen King said: "Harry Potter is about confronting fears, finding strength and doing what is right in the face of adversity. Twilight is about how important it is to have a boyfriend.") But you suspect that Pattinson recognised the limits of Twilight long ago.
In May he starred in the Depression-era romance Water for Elephants. Next year he'll appear in Bel Ami, which will involve him being a thoroughly bad egg and sleeping with Christina Ricci, Uma Thurman and Kristin Scott Thomas. And then there's David Cronenberg's adaptation of the Don DeLillo novel Cosmopolis, about a cheating Manhattan billionaire who loses his fortune in a single day. He has described the script as "insane and difficult"; the cast includes Samantha Morton, Paul Giamatti and Juliette Binoche. It's the big league, by any standard. More the choice of an actor seeking a challenge than a pretty boy looking for safe harbour.
"If I do decide one day to stop acting, I just hate the idea of people going: 'Oh, did you ever do anything else besides that Twilight thing?"'
LOWDOWN
Who: Robert Pattinson
What: Breaking Dawn - Part 1, the fourth and penultimate movie in the Twilight series
When: Opens at cinemas November 17
- TimeOut / Observer
