Shia says training would not have done any good. "I’m not playing a Gladiator, just an ordinary kid in an extraordinary situation," he says.

"The only training I did was I smoked cigarettes at the time and started chewing tobacco and sunflower seeds."

One of the attractions of the sequel was reuniting with film- maker Michael Bay, who he’ll work with again on the third Transformers movie, due out in 2012.

"It was terrific," Shia says, grinning. "Michael and I are like big brother, little brother. He’s like a football coach, and he doesn’t coddle you. That takes getting used to – a lot of actors are used to being coddled, but I enjoy the hell out of it. It’s like sky-diving for five months."

Not to mention that he gets to kiss two gorgeous women – Megan Fox, who plays his on-screen girlfriend Mikaela, and Isabel Lucas, a fellow university student who fights for his attentions.

"I’m the luckiest dude in the world, clearly," he notes, before adding: "I think there were two kisses in it, not a lot. Super scary kisses."

Having been in the spotlight since childhood, which he admits was impoverished with his divorced parents, Shia is understandably reluctant to embrace fame and fortune.

He prefers to keep his personal life to himself, staying away from the Hollywood party scene. He lives in a modest two-bedroom house near his mother, to whom he remains close.

While he may enjoy the attention that Transformers has brought to his career, it seems that he can’t always escape the attention the film has brought to his life off-screen.

In November 2007, he was arrested for an incident in a Chicago pharmacy, and last July he was involved in the car crash in his home town.

"I’ve had to deal with all different types of situations – positive and negative and extremes of both," he admits.

"I didn’t read the book on how to be a well-adjusted celebrity. I still haven’t figured out that I’m a star yet."

He dismisses any suggestion that he’s made his career through talent. "Talent seems like a crazy- ass word," he says.

"I just think determination is a better word. It’s like boxers, who are ordinary men with determination. Talent is a crazy word, it seems weird."

He adds: "I’m very fortunate. I’m not the most gifted performer in the world, just very lucky to be given these opportunities. But I’m not in this to get successful. I’m happy, and I need to keep working."