IT'S almost impossible to resist Zac Efron's boyish charms.
Even if you're not a fan of High School Musical, the Disney Channel series that turned him from unknown teenager into hunky heart-throb, it's easy to see why scores of teenage girls have waited outside a London hotel for hours, just to catch a glimpse of him.
Even with the fingers on his left hand bandaged up in gauze, which he jokingly blames on an over-zealous fan, Efron oozes sexiness in a custom-made black suit and fitted white shirt. And with his slicked back brown hair, one lingering gaze with those piercing blue eyes is enough to reduce most grown women – and some men – into giddy teenagers again.
His post-High School Musical moves have been eagerly anticipated, as people watched earnestly to see how the 24-year-old would shake off his Disney role. And while each film – from The Life And Death Of Charlie St Cloud, Me And Orson Welles and New Year's Eve – has taken him further away from those teenage outings, his latest movie, The Lucky One, could arguably be his most mature yet.
In Scott Hicks's big-screen adaptation of the Nicholas Sparks novel, Efron plays US Marine Sergeant Logan Thibault, who returns home after serving his third tour of duty in Iraq.
"Initially, I wasn't convinced I could pull this off, but the more I thought about it, and the more I talked to Scott, I realised if there was ever going to be a chance to play a role so different from what I've played before, this was it," says Efron.
Playing a soldier suffering from post-traumatic stress disorder (PTSD) is new to the actor, who has never strayed too far away from his comfort zone. To make sure he was doing the part justice, he took the opportunity to speak to real-life marines at Camp Pendleton in California.
"It was like stepping into a different world. They were very normal guys other than their posture and the way they present themselves: they stood with a purpose, they had laser focus and never broke eye contact," he recalls.
"They had immense dignity. Never once did they let on how traumatising it was until they started telling their stories, and even then it wasn't weepy, you could just see it in their eyes that they had been there and experienced some pretty gruesome things."
Next came the physical transformation: gone is the floppy, boyish hair, replaced by a buzz cut.
"It was pretty symbolic cutting it all off. Boy, was that weird! But it was a really great feeling," he says.
Efron had to undergo gruelling training with retired Sergeant Major James Dever for four months to pass for a seasoned marine.
"It was the most intense training I had ever done," he says.
Fans will also see a whole new side to Efron in the film, as he strips off for his first steamy love scene.
How does he feel about the hysteria that happens every time he shows a bit of skin?
"I don't really know how to put it into words. It's better than the opposite reaction," he admits, focusing on straightening the tablecloth.
"I try not to think about it at any point. That's one thing I don't notice; I'm looking at all the flaws. I'm looking at the performance more until my mum says very loudly, 'That's my boy!' Then you go, 'Oh, my God'."
He gives due credit to leading lady Taylor Schilling, saying: "Heck, I had a great partner – we kind of got lost in it.
"I thought she was beautiful when I first met her. She's unafraid of trying anything, she's very good to work with."
As for the sex scenes, being surrounded by a nervous crew and having a relaxed director helps dispel any awkwardness.
"Everyone is tense on those days, it's not just us. It's kind of like a built-in awkwardness," says Efron, lowering his eyes.
"Taylor and I knew each other very well by this point. I tried to make her as comfortable as I could, which was just to laugh it off."
While Efron, who previously dated his High School Musical co-star Vanessa Hudgens, admits to being more "easy-going and gregarious" than "serious" Logan, it's clear that he's taking time to make the right career moves and has set up his own production company, Ninjas Runnin' Wild, under Warner Bros.
"I want to make cool movies that I would watch. Anything that's innovative, that's new," he explains.
Efron will next be seen in Josh Radnor's indie drama Liberal Arts, which premiered at Sundance London, and he's off to Cannes for Lee Daniels's The Paperboy.
Efron, who counts his family as his lucky charm, believes destiny has played a part in his life.
"I know that I was in the right place at the right time and there are moments when I just think: 'It's too good to be true'," he says.
"Maybe fate presented me with opportunities, but it's the hard work that gets you the right film."