Robert Pattinson in Budapest, filming a scene in his new movie Bel Ami . Picture by AP

The phenomenally successful teen vampire franchise, Twilight, has sunk its teeth into a hungry fan base and transformed Pattinson from a bumbling Harry Potter supporting cast-member into one of the most desirable men on the planet (or ‘the Most Handsome Man in the World’, as he was dubbed by Vanity Fair).

It’s earned him millions, made British-born Pattinson the most sought-after young actor in Hollywood, and furnished him with a superstar girlfriend, his co-star in the vampire films, Kristen Stewart.

But the success of the first two instalments in the franchise — Twilight, which came out in 2008, and New Moon, which was released last November — has engendered its own set of problems, not least on the set of his first post-Twilight movie, Remember Me.

“Honestly,” begins Pattinson when we meet up in a hotel in London, “shooting Remember Me was really difficult. The Twilight fans were great — they’d come, watch us shoot and would be quiet when they were asked — but the paparazzi, what a bunch of f***ing animals.”

Pattinson explains that the photographers made so much noise — shouting out, trying to ‘get a rise’ —that the cast’s dialogue was ruined, and had to be completely re-recorded.

Then one punched the second assistant-director in the face. “That was a bit much,” Pattinson says.

This is the fifth time I’ve met Pattinson, and each time he’s been bashful, humble and fun to be around — almost too fun. So at pains is he to be personable and rip-roaring company — the polar opposite of Twilight’s dour, broody 100-year-old vampire, Edward Cullen —that his efforts often horrify those around him.

Shortly after landing the part, he admitted that he’d taken Valium in order to get through the Twilight audition. Last year, apropos of nothing, he whispered in my ear: “Honestly, I just went for a pee and suddenly about 20 people wanted to shake my hand straight away. I was like, ‘Hah, hah, I haven’t even washed my hands!’”

His publicist was mortified. It’s easy to imagine a similar reaction to a recent interview in which he joked that he was “allergic to vagina”.

Today, he is sporting a raggedy beard, which he’ll wear during his next non-Twilight movie, Bel Ami, a fan base-testing adaptation of the second novel by 19th-century French writer Guy de Maupassant. “It’s awesome,” Pattinson laughs. “Christina Ricci, Uma Thurman and Kristin Scott Thomas, and I sleep with all of them!”

Just a few years ago, Pattinson was yet another actor-cum-model-cum-musician with a few solid, if unexceptional, roles to his name — one of which, Mira Nair’s 2004 version of Vanity Fair, actually ended up on the cutting-room floor.

Today, at just 23, he sits atop a film franchise that is expected to make in excess of £1.3 billion by the time it ends. He has already filmed the third in the series, Eclipse, and will shoot the fourth and final chapter, Breaking Dawn, at the end of the year.

The hysteria he causes wherever he goes is often compared with that which followed Titanic-era Leonardo DiCaprio, but, if anything, it’s even more frenzied. During filming and at premieres he needs a team of 25 bodyguards to protect him from the braying mob. When they do manage to get to him, fans regularly present him with vials of their own blood, or invite him to nibble their necks.

There are currently six unauthorised ‘R-Pattz’ biographies in publication, and there will probably be a couple more by the time you read this. Recently, Pattinson’s life story was retold in a documentary, Robsessed, featuring interviews with friends, former teachers and ‘super-fans’. Robsessed 2 is already in the works.

And the Robert Pattinson fever is not being fed by teenage girls alone; it’s their mothers, too. Middle-aged, middle-class fans have even formed their own splinter group of ‘Twilight Moms’, who claim the books and films have helped improve their sex lives.

Stephenie Meyer — herself a middle-class, middle-aged mother — imagined E29hollydward Cullen as ‘the most beautiful creature who has ever been born’, an impeccably mannered, almost impossible-to-realise cross between Adonis and a Jane Austen heart-throb. Prior to auditioning for the role, it’s safe to say that Pattinson did not fit this description.)

His most high-profile part had been the doomed Cedric Diggory in Harry Potter and the Goblet of Fire. His agent encouraged him to find similar high-profile roles, but Pattinson opted for a part on stage, taking the lead in a Royal Court production of The Woman Before. The man he played was supposed to be troubled, so Pattinson decided he would “do something really weird”. But his over-acting didn’t go down well and he was fired shortly before opening night.

He then went “nuts” and considered giving up acting altogether. Apart from roles in How to Be, a BBC drama called The Haunted Airman and Little Ashes (in which he played Salvador Dali during a stormy affair with another man), by the time he auditioned to play Edward Cullen, in 2007, he’d been trying to break into music and “getting drunk for a year”. But the producers opted to ignore his beer paunch and the part was his.

“The fans were asking for people like Leonardo DiCaprio,” he recalls. “And when you consider how gorgeous my character is in the books, I was put off. I thought no way could anybody play this guy.”

When Pattinson’s casting was announced, the books’ 17 million-odd fans duly erupted with such hatred you’d think the filmmakers had picked Ronnie Corbett. Pattinson’s mother kept calling to tell her son that he was being called ‘too old’ or ‘too ugly’ all over the Internet.

Pattinson has changed little since his Harry Potter days and is living proof,

perhaps, that good things come to those who don’t desire too much. An aw-shucks modesty has become part of Pattinson’s shtick. He’s positively embarrassed by his looks, or at least affects to be.

“I have been lucky, of course,” he says. “Like, last year, if I went out, I’d have to fight to chat someone up. This year, I look exactly the same, which is really scruffy, and yet lots of people seem to have just changed their minds and decided I’m really sexy.

“Basically, anyone who wants to be seen as attractive should just get Stephenie Meyer to say: ‘This guy is attractive.’ Then everybody believes it.”

Pattinson grew up in the bucolic London suburb of Barnes. His mother, Clare, worked for a modelling agency, while his father, Richard, is a vintage-car dealer. He is the youngest of three children; Elizabeth, a musician, is 26, and Victoria, who works in advertising, is 31. He attended Tower House prep school and then the Harrodian School.

“I never really did much acting back then,” he says. “But one day my dad and I were in a restaurant and he saw this bunch of pretty girls and he asked them where they had been. They said that they went to this drama club, so he said we’d better go down to this drama club, too.”

A part in Thornton Wilder’s play, Our Town, soon followed, as did an agent. Up until that point Pattinson, like his sister Lizzy, had harboured musical ambitions. “I wanted to play piano in restaurants in the south of France. I went there on holiday once and I saw this guy playing in an old tuxedo. He was all dishevelled, with a whisky glass on the piano. I thought that was the coolest thing. So what’s happened to me with Twilight isn’t really what I’d planned.”

He’s a gifted piano and guitar player, and is so obsessed by Van Morrison that he dreams of playing him in a biopic. Right now he’s composing music for a film he’s not in, whose name he can’t reveal because “I might not have time to finish it.”

Despite — or perhaps because of —the £12 million he’s so far made from Twilight, Pattinson seems blissfully unconcerned with how his career will pan out. He lives in detritus-strewn hotel rooms, stays with his parents when in London and claims to have absolutely no material needs beyond his “crappy car” (a 1989 BMW convertible). That said, he is keen not to become the next Orlando Bloom, an actor who has struggled outside of a big franchise that requires him to do little more than look sexy.

“Sure, I hope that Remember Me shows I can do more,” he says, “although I see all these things saying the film is a test of whether I can act or not, but what do you think I’m doing in Twilight?”

After shooting the final Twilight film, Pattinson is due to begin work on Unbound Captives, a western. He chose the latter because his father is “obsessed” with the genre, not because it’s going to be easy: “It’s going to take at least a month or a month and a half of prep work. My entire part is in Comanche. I need practice.”

For now, there’s Remember Me, a romantic drama about Pattinson’s strained relationship with his father (Pierce Brosnan) and his nascent romance with Lost’s Emilie de Ravin.

As the film progresses, the audience comes to realise that this is 2001, and September 11 is looming. In the United States the film’s ending has been called emotionally manipulative.

“I had been warned about people thinking that, but I read the script, and I just thought it was very tragic. I like the sense of foreboding.

“I suppose I could’ve been typecast after Twilight,’ he continues. “The good thing is that the economy is so bad, I can go, ‘I don’t care if you think I’m right for it, I can get your movie made!’” He laughs. “No, seriously, I’ve never said that in a meeting.”

One subject on which Pattinson has been shockingly tight-lipped is his romance with Kristen Stewart. Theirs is one of the most dissected and speculated-upon relationships of recent times, and in an age in which mobile phone paparazzi lurk around every corner, you can’t help but admire the way the couple have controlled the media coverage.

“I do think Kristen is amazing,” is all he’ll say. “I wanted to work with her the moment I met her. Our chemistry was so good.”

Their relationship blossomed while they were shooting the first film. Stewart was still in a relationship, but Pattinson concedes that he pestered her from the outset. “I asked her out a lot but she wasn’t having it.” Eventually, she relented.

The pair kept their relationship secret throughout the filming of New Moon. Pattinson, according to the gossip press, was linked with the likes of Camilla Belle, model Anne Schoenberger and former flame Nina Schubert, skilfully deflecting attention from Stewart.

Recent reports suggest Pattinson and Stewart have been house-hunting on the Isle of Wight. The couple spent New Year’s Eve in Ventnor and have apparently been looking for a love nest ever since. It would certainly tally with Pattinson’s desire for normalcy and anonymity, which is genuine if his wistful recollection of a trip to Oxford Street last Christmas Eve is anything to go by.

“No one recognised me, even though the store was full of New Moon posters. It was great. It’s harder in America. I can’t do anything there. There are all these screaming fans. But if I talk to one for five minutes, the illusion is gone.”