Faith in Hollywood: Paul Greengrass, director of 'Green Zone

As a broad smile spreads across his face, Paul Greengrass's pleasant demeanour goes against everything we've heard about his enfant terrible reputation. Polite, thoughtful and articulate, the 54-year-old Englishman is a filmmaker never afraid to address uncomfortable subjects on screen, tackling some of the darkest moments in modern history and recreating them for the celluloid world. Starting in documentary film, he took those skills to television drama. He co-wrote a film about the Omagh bombings in Ireland, and directed Bloody Sunday, a film intended for television but brought to cinemas after a tremendous reception at the Sundance film festival.

Hollywood came calling, and he began his collaboration with Matt Damon in the two sequels The Bourne Supremacy and The Bourne Ultimatum. His highest note perhaps has been receiving a Best Director Oscar nomination for United 93, a film about one of the aircraft hijacked during the September 11 attacks. His latest work is his third with Damon, the Iraq war thriller Green Zone, an adaptation of the book Imperial Life in the Emerald City, about a warrant officer (Damon) searching for weapons of mass destruction in the aftermath of the 2003 occupation of Iraq.

The film's box-office takings will undoubtedly be compared with those of the Bourne franchise. Coming hot on the heels of the phenomenal success and Oscar glory of the The Hurt Locker, another Iraq war movie, also raises expectations. Greengrass is well aware of the risks of this project. "I can't pretend it isn't an issue, but we used it in the sense that it became part of what we were trying to do," he explains.

"After The Bourne Ultimatum, the challenge for me became, could we bring that audience to this subject matter? It's important to me that cinema has those types of films - films that reflect what's going on and comment on the world we live in. Of course, they can't all be like that. Cinema is also a place for escape, a place for dreams, but we need to have those big movies, the 'tent poles' as I call them, that represent what's happening in the world."

He is also very optimistic about the future of Hollywood, believing the quality of big films is rising in places. "Look at The Dark Knight," he says. "That was an incredibly successful film financially, but also in my opinion one of the best movies of the past decade. Those themes of darkness, violence, insanity were all very powerful, but can exist within this movie about Batman. "What they did was offer a rewarding experience to a wide audience by making a film they could identify with. It's not present in all mainstream cinema, but films like that show it can be done.

"This is a different film, but we think we've got that mix - a great story, and a fantastic actor doing what people love to see him do. When people come to the cinema they will be rewarded by seeing our film, but also it will make them talk when they leave the cinema." It's a mix that is headed up by both Greengrass and Damon, who first worked together on The Bourne Supremacy in 2004. A sequel to The Bourne Identity, it was a huge hit worldwide and elevated the filmmaker from the world of independent film to one of the most coveted directorial talents.

The pair have reunited twice, and the secret to their success is very simple. "He's very good at what he does," the director says. "With any director it's important to have an actor who both inspires trust and is capable of the type of performance you are after. In Matt you have, as I've said, the biggest movie star in the world and someone who understands the world of his character, and conveys what his character is going through."

With the huge success of their previous two films together, Greengrass has been hounded by the question of whether he would be interested in making another Bourne film in the future. Although he has said that he in fact won't be returning, he acknowledged the great boost it has given him and his star. "That's a franchise that is very dear to me, and one that I'm incredibly grateful to for all the success we enjoyed with those films."

In addition to acting talent, a big part of the filmmaker's arsenal is the work he has done with Barry Ackroyd, a British cinematographer famous for his fraught, kinetic, "anti-Hollywood" style, which gives the projects he works on the feel of a documentary. As well as working with Greengrass on this film, he also notably worked on The Hurt Locker. "He's brilliant," the director beams. "It delights me to see that he's getting the recognition he so clearly deserves. I've worked with him before, on United 93, and I think I'll always be grateful to him for the bravery of his choices when we were working together. We shot the whole final-night sequence 'real', without any lights, and Barry was up for it whereas many DPs would have thought it was too risky. That's something we share - a passion for a realist, documentary-style of telling these stories."

Another thing they have in common is an attraction to "risky" subjects. Greengrass's United 93 was an unflinching account of the hijacked airliner that crashed outside Washington during the September 11 attacks when the passengers atempted to seize it back. It was the first Hollywood film to address the attacks directly, and was released just under five years after them, drawing criticism from many for portraying an event that was still raw in the minds of many Americans.

"Some might think this [Green Zone] and United 93 controversial, but to me it's just my job as a filmmaker. My roots are in social documentary, of creating a dialogue about what happened and offering a certain perspective, which is fictional but based on the accounts of people who were around in that world at that time. This film doesn't tell people what to think, and neither did United 93, but it tries to capture what was really happening in the eyes of the people on the ground, so to speak."

The film has, in some ways, done exactly what Greengrass hoped it would, as many have debated the message behind the film. Many have called it "anti-American" and inflammatory; however, the reviews from critics have been largely positive, praising the filmmaker's ability to weave a fictitious tale into a real-life setting. The box-office reception in America has been similarly positive, with early reports stating Green Zone has made $14.5 million (Dh53m) in its opening weekend, a very strong figure in comparison with other war films.

Finally, does the director believe the former British prime minister Tony Blair and the former US president George W Bush should watch this movie? "I'm sure they would find it very entertaining," he smiles. "In fact, I'm thinking about setting up a screening!"