Hero or villain, clever or clueless, war champion or criminal, it’s hard not to have an opinion on President George W Bush.

During eight years in office, he’s been the butt of a slew of jokes, with his legendary mispronunciation and Texan drawl. His decision to go to war with Iraq, reaction to Hurricane Katrina and his leadership of a country in mourning after 9/11 have made him one of the most talked about presidents in recent history.

Not one to shy away from controversial subject matter, director Oliver Stone has attempted to put a human face on the much-maligned leader of the free world in his new film W, handing actor Josh Brolin the arduous task of playing the president.

“When Oliver first approached me, I thought, why would you want to do a movie about that, when you can watch this guy on CNN? I had a very cosmetic view of Bush, and Oliver,” 40-year-old Josh admits.

“Oliver has a very controversial reputation, which I found out later is superficial. So my perception about him – and, as it turned out, about the movie, was totally wrong. But initially I said no. I told him I would love to work with him, but I just had no interest in going there. And the fact that Oliver was even seeing any kind of connection between me and Bush was slightly insulting. Oliver, instead of being put off by that, was intrigued. He said ‘just read it’. So finally, I did. I was taken aback, moved by it – impassioned and saddened. And above all, I identified with it.”

With films like JFK and Nixon to his name, Stone’s W is the first-ever movie about a sitting US president. Perhaps unsurprisingly, Bush declined to be a technical advisor on the film.

“Usually when you do a biopic, you cover about 10 years of a life, but here, you go from 21 to 58,” says Josh.

“I was thinking ‘Can I live up to it?’ I just spring-boarded from a lot of fear. I think it was based on fear of pulling it off.”

Certainly, the movie sees Bush go through a multitude of changes – from his youthful days as a hard-drinking party animal to his conversion to Christianity, newfound sobriety and decision to run for president. His later years, as covered in the film, follow his administration’s discussions over the war on terror. But it was Bush’s early life that intrigued Josh the most. “We played with the idea of, well, what was he like in his hometown of Midland, Texas?” he says.

“Did he do all that stuff as a young man? Was all the stuttering and breathiness caused by tension? Did it increase in office? How much is too much? This is our version of George W Bush and his life. It’s worth doing,”

Josh is joined in the film by a strong ensemble cast that includes Elizabeth Banks as wife Laura, Thandie Newton as Condoleeza Rice, Richard Dreyfuss as Dick Cheney and James Cromwell as George Bush Sr.

Stone says “Josh gives the great performance of his life” in the film and early reviews in the US have added to the plaudits for the actor.

“The thing about this president is he is an exaggeration of himself, even that he admits,” Josh says.

“It’s fun to watch. What we’ve tried to do is create a drama with the realities of those exaggerations but not making it into buffoonery. I don’t think we did. They’ve done that themselves, but we haven’t.”

Then there are the comic touches in the film. Bush’s mispronunciation of words, the infamous pretzel choking incident and his constant eating – all moments which Josh says adds colour and depth.

“Bush is an exaggerated personality. There are gestures of his that you can’t deny and are hilarious. That’s why there’s so much cartoonish impersonation of him. So when you’re doing the movie, you’re searching for the tones and you don’t know what it is. And what we’ve come up with is a very dramatic version, with comedic overtones. It allows you to breathe.”

Last year’s starring role in Oscar-winning No Country For Old Men cemented Josh’s reputation for handling demanding roles. After W, he appears in Sean Penn’s movie Milk.

Although he is looking to the future, playing Bush will stay with Josh for a long time yet.

“Ultimately it was the most fulfilling role I have ever done,” he says.