Then again, you suspect he's seen a lot of bizarre things in his time since exploding on to the scene as teen vampire Edward Cullen in the mega-hit Twilight franchise. That was six years ago, during which time he's got used to seeing gaggles of screaming girls wherever he goes. Heaven knows what they made of the recent black-and-white Dior Homme commercial he shot - a sizzling, sexy spot scored by Led Zeppelin's Whole Lotta Love. Maybe that's why he has that permanently dazed look.
Today, he's looking relatively unscathed by the fame that follows him like a familiar. It might be close to 6pm, but Pattinson has a brilliant means of affecting that just-got-out-of-bed look. Dressed in beige trousers, a green-and-navy lumberjack check shirt, black Adidas trainers and a black bomber jacket, it's a casual street feel that suggests more Urban Outfitters than Armani Couture. Factor in the stubble, sleepy green eyes and tousled hair and it's like he's splashed on eau de hipster.
With two new films to bang the drum for - The Rover and Maps To The Stars - it's Pattinson's second time in Cannes in two years, following his arrival as a limo-dwelling billionaire in David Cronenberg's Cosmopolis. That was a turning point, he says. "I'd never even been to a festival before. It makes you think differently about things. You realise what you like. Cannes means a lot to me. I'm basically aiming for everything to get into Cannes."
At 28, this boy from Barnes, in south-west London, is craving credibility. "Rob really fights to be seen as an actor, rather than just as a movie star," says director Anton Corbijn. "He's really trying to prove his worth."Corbijn has just finished working with him on Life, which casts Pattinson as photographer Dennis Stock at the time he undertook an assignment to shoot a pre-fame James Dean. Looking down the lens, rather than being deluged by flashbulbs, was doubtless intriguing. "It was interesting for him to be on the other side of the camera for once," adds Corbijn.
Of course, it's been difficult, given his on-off romance with Twilight co-star Kristen Stewart. Two years back, the media-crowned R-Patz and K-Stew were in Cannes together. "It's nice to have someone who is really ambitious and has good taste," he told me at the time. "I've always liked my friends and people around me to be quite good pacemakers. You don't want to have a bunch of arse kissers around. You want it to be a competition. You want the people you respect to be good."
Then the unthinkable happened. Stewart was snapped kissing Rupert Sanders, her (married) director on Snow White And The Huntsman. It virtually kept the gossip rags afloat for that summer, as Pattinson moved out of their LA home and went on Jon Stewart's chat show (where the host brought out Ben & Jerry's ice-cream to console him). After reportedly getting back together, and overlooking her "momentary indiscretion", they finally split in January last year.
More recently, Pattinson has been linked to just about every A-list starlet going - from model Imogen Kerr to musician Katy Perry and actor Riley Keough, who happens to be Elvis's granddaughter and a friend of Stewart. Naturally, Pattinson is coy on the subject of his singledom, but he's still willing to talk about Stewart - at least when it comes to their work ethos. "I think both of us have had pretty similar ideas about what we want to do. I think. Well, actually I didn't … I didn't really know what I wanted to do until two years ago."
Smartly, the only relationships he's building right now are with directors, meeting and greeting even before scripts are on the table. "I got sick of just waiting for something to happen," he says.
Strangely, despite his unfathomable levels of fame, he's not the sort of actor the Hollywood studios have come calling for to front huge summer blockbusters. "Maybe after the first Twilight, I had offers for that kind of stuff, but I've never really been part of the group that gets offered that stuff. You get quite defined by Twilight in terms of big franchise stuff."
It seems the intensity of the Twilight years has sent him searching for more soulful, adult experiences - as demonstrated by his two new movies. In The Rover he teams up with Guy Pearce for an apocalyptic Australian tale set 10 years after a global economic meltdown. Taking place in an arid landscape full of scavengers and thieves, the film begins with Pearce's character Eric seeing his car stolen. Refusing to relinquish his possession, he gives chase - and along the way meets the slow-witted Rey, played by Pattinson.
The pair form an uneasy bond in a world of chaos. It's a unique role for an actor usually cast as either the romantic hero (Twilight, Water For Elephants) or the arrogant alpha-male (Cosmopolis, 2012's Guy de Maupassant adaptation Bel Ami). When writer-director David Michod met Pattinson, he hadn't seen the Twilight films. "Still haven't," says the director, smiling. "I just met him while I was meeting all sorts of people in LA and I really liked him. He came in to test for The Rover and I knew almost immediately that I'd found my Rey. It was as simple as that."
Shot in Australia's Flinders Ranges in scorching temperatures, Pattinson says he revelled in the discomfort. "If you're trying to do something where you weren't playing someone who is filthy and disgusting all the time, then it would have been annoying - if you had someone [from the make-up department] constantly getting rid of your sweat. But when you can wallow around it, it's nice." Pattinson, it should be noted, once admitted to Jay Leno that he rarely washes his hair. "There's a scene - me and Guy up against a fence. I remembered it; we'd both been out in this ridiculous heat and kind of being a bit insane, and I realised it just wasn't make-up any more. We were both so sunburned and looked like such shit. And even the look in your eye … there wasn't anything to eat out there either, so I was literally eating pieces of bread with barbecue sauce on, for six weeks. I was turning into a lunatic."
Michod, for one, is aware that The Rover is not your usual R-Patz fare. "I don't know what his fans will make of the movie," he shrugs. It explains why Pattinson was desperate for the role. "I've never worked so hard for an audition. I was obsessed with it. But once I got the job, I've never felt more free in a part. There were no constraints to it at all. The first thing I asked David was, 'Is Rey mentally handicapped?' And he said, 'I don't know. Decide.' It was really open."
His second new film, Maps To The Stars, sees a reunion with Cronenberg - proving again that in showbusiness it's not what you know. "He just offered it to me. I hadn't even seen the script, but I was like, 'Yeah, definitely.' I like him and I like all his movies."
A venomous Hollywood satire that deals with the warped and corrosive nature of fame, it's one of the best-written pieces you'll see all year, not least as it showcases Julianne Moore's Cannes-winning Best Actress performance as Havana Segrand, a desperate Hollywood has-been.
When Pattinson finally did read the script, he was immediately taken. "It's the weirdest story in the world,"he smiles. He plays the brilliantly-named Jerome Fontana, an aspiring actor who makes his crust driving a limo (presumably a sly nod to his Cosmopolis role) and befriends Mia Wasikowska's character - a shy, disfigured girl who arrives from out of town to become a personal assistant to Havana. One of the most eye-catching scenes, however, sees Pattinson and Moore enjoying athletic sex in the back of his limo.
It's not his first time at this particular rodeo, having enjoyed more than his fair-share of limo-bonking in Cosmopolis - notably with Juliette Binoche. "None of them were supposed to be sex scenes, and he [Cronenberg] changed them all afterwards," he protests. "I always find sex scenes are the most random thing to see in a movie. Two actors pretending to have sex. Why? It's so stupid." Quite whether this means he'd like to eliminate sex scenes from movies or indulge in authentic copulation on screen is not clear.
Presumably it's the former - given the experience he had with Moore on Maps. "That was kind of hilarious. That was the first time I'd met Julianne as well. It was so hot in Toronto [where the film was shot], and she's one of these people … she doesn't sweat at all. But I sweat like a crazy person. And I was trying to literally catch drops of sweat from hitting her back. It was so embarrassing. Afterwards she was like, 'Are you OK? Are you having a panic attack?' It was so embarrassing."
Still, at least the scene will help stamp out those silly rumours questioning Pattinson's sexuality after an interview he gave to the US magazine Details when he spoke with Jenny Lumet, who worked uncredited on the script of 2010's Remember Me, a romantic drama set in the build-up to 9/11 starring Pattinson and Emilie de Ravin. In it, in reaction to the magazine's photo shoot that put him among a cluster of naked models, he claimed he was "allergic to vagina".
Ironically, it was as a means of meeting girls that Pattinson's father Richard encouraged him to act. He joined an amateur group, Barnes Theatre Company, and was soon cast in a role in a production of Guys And Dolls. Both his father, who ran a business importing vintage cars, and mother Clare were immediately encouraging. "When I was not trying very hard at school, my dad was like, 'Just leave school and get a job.' No-one ever said, 'You need to do your exams.' It was more like, 'If you're not going to take advantage of things, don't do it. Do so something else.'"
Pattinson's upbringing alongside his older sisters Lizzy and Victoria sounds harmonious. His mother used to work at a model agency - and the teenage Pattinson began by getting work in this field (though he later claimed he had "the most unsuccessful modelling career"). His first acting break didn't exactly go to plan either, as he was left on the cutting room floor of Mira Nair's 2004 adaptation of Vanity Fair. A year later, however, he was cast in Harry Potter And The Goblet Of Fire, playing the handsome Quidditch star Cederic Diggory. Around the same time, he was due to appear in a Royal Court production of The Woman Before, but was fired before opening night and replaced by Tom Riley.
"Getting fired from that was probably the best thing that happened to me because I was going around saying 'I'm such a firebrand, such a rebel. I got fired because I wanted to keep my integrity as an actor.'" He almost blushes at the recollection. "I just remember saying so much bullshit to people afterwards."
It's moments like this that make Pattinson such an engaging and honest interviewee. He recalls the aftermath, auditioning for A Few Days In September, a Juliette Binoche movie. "I wanted it so bad," he recalls. But, to rub salt into the gaping wound, the role went to his replacement on the play, Tom Riley. "Because Tom replaced me so close to the play going on, there was a really good review of his which [mistakenly] said it was me. So I took it to America with me, and I was like, 'I've been doing theatre.'"
Thankfully, his saviour came in the shape of Edward Cullen. "If I hadn't done Twilight, I'm not even sure if I'd be acting any more. I was doing jobs for £500 for four months." He cites Little Ashes, in which he played Picasso. "I got Twilight afterwards, completely by fluke. I had no money, and I had to pay a tax bill." Now it's so different - with an estimated fortune well over £40 million. While Time magazine placed him among their 100 most influential people list, a Russian astronomer even named an asteroid he discovered as 246789 Pattinson.
In all this time, Pattinson hasn't stopped challenging himself. You'll next see him playing Colonel TE. Lawrence, made famous by Peter O'Toole in Lawrence Of Arabia. The film is Queen Of The Desert, which tells the story of English writer, traveller and archaeologist Gertrude Bell, played by Nicole Kidman. "Obviously it's big shoes to fill, but it's not like I'm playing Lawrence of Arabia," says Pattinson. "It's Gertrude Bell's story, and Lawrence was just … they were just friends. They were best friends for a period."
There's talk too that he might team up with Robert De Niro in Idol's Eye, the story of a gang of crooks robbing a pawn shop. While that might be a daunting prospect, there's a relish in Pattinson's eyes; he's finally being accepted as an actor, not a tween heartthrob. As a result, he's been able to banish self-consciousness. "You find it a lot in acting, especially when you feel the need to prove yourself all the time. The main enemy is getting trapped within yourself. It happens all the time."
The Rover (15) opens on August 15. Maps To The Stars (cert TBC) is released on September 26.