Oliver Stone seems wired, if not spaced. “Tension! Are you kidding? This is my first time on the red carpet. I never saw a red carpet like that before. This is official. I’ve only been in competition two or three times.” Stone has just arrived for lunch at the Eden Roc restaurant in the Hôtel du Cap, Antibes. The night before, with Charlie Sheen and Willem Dafoe, he had introduced a special Cannes festival screening of his 1986 film Platoon. He had also shown 25 minutes of his new 9/11 film, World Trade Center. But he doesn’t seem to remember anything about the event.

I ask him, for example, why he apologised for the new movie’s special effects “looking like Japanese sci-fi”. To me, they looked impressive.

“Did I say that? Is that right?” He was, apparently, overwhelmed by the red carpet and stuff. “I had to buy a bow tie! There’s something about that moment, going up those steps. Every time you do something like that, it’s a key event. In America, it would be the Oscars or something. Actually, I’d been rejected maybe four times by Cannes. Natural Born Killers won the prize here — that was my last experience of festival politics. After that, I never came back.”

I had not expected this. The pugnacious outlaw director seems nervous, almost cowed. This impression is reinforced when, some days later, his people ring The Sunday Times to check if the interview was okay: “He liked Bryan, but...” Perhaps he’s always like this; or, more likely, he’s edgy because this is his first film since Alexander, a costly turkey, at least in America. “I got off on the wrong foot in that first scene that has snakes in the bed. People were taken aback by that. That’s not going to go down in Ohio.”

It was hurtful because Alexander was his big pet project. “My whole life I’ve been fascinated by history. I love the past. I loved doing Nixon, going back to my you... And Alexander’s mind! He was the proto-original to me. Nobody had thought of organising the world. Alexander was the first westerner who really went to the east. He didn’t come back with the loot, he stayed, he became eastern. It’s the ultimate merging of the two, it’s the world order, the world-government concept.”

Never mind. The Cannes crowd — dreadful people, but they do love their movies — were crazy about Platoon, Stone and the boys, and they roared their approval of the World Trade Center footage. The film, which opens in America on Friday, is the true story of the police “first responders” who went into the Twin Towers after the planes hit. In particular, it’s about officers McLoughlin and Jimeno (Nicolas Cage and Michael Pena), who get trapped under the rubble when the first tower collapses. It’s a tricky subject, technically, as the audience knows exactly what’s going to happen.

“It’s a classic movie thing, isn’t it? Hitchcock did that — you know what’s going to happen, but you have to make it suspenseful and exciting along the way, even if you know whether the men are going to live or die. I was powered along in United 93, though I did know it wasn’t going to end well. I wanted to know more.”

Trickier still is the whole issue of how to handle 9/11. I mention Steven Spielberg’s comment to me — that, as with Vietnam, it will be some years before the big movies emerge, though, along the way, we might get straight macho stuff like The Green Berets. This is probably a ghastly faux pas, as Stone looks as if I had implied that WTC was like The Green Berets. Not what I meant at all.

He launches into a complex — and unnecessary — justification, hinging on his belief that 9/11 has had its Green Berets phase on TV, with programmes such as Rescue Me. But he also points out that 9/11 remains much more of a mystery than people realise. “We don’t know what happened, really. We never investigated it. They spent more money investigating Bill Clinton’s blow job than they did 9/11.”

This is Stone at his most familiar. Obsessed with conspiracies and concealment, he remains convinced that the thesis of his film JFK, that there was some kind of wider plot to kill Kennedy, is correct. This approach to history constantly lands him in trouble, and he’s sensitive about the criticisms. “Historical issues have dogged me my whole life. I loved history in school. I’ve studied and read so much history. I think I have a grasp of what it’s like, and Oliver Stone did not invent the mixture of fact and fiction — that’s the accusation my detractors make. JFK was based on years of reading.”

Through that film — as well as Nixon, Born on the Fourth of July and even Natural Born Killers — Stone has become the cinema saint of those who take the paranoid view of America as a malign conspiracy. I ask if the problem is that he’s actually a disappointed patriot. “I know where you’re going with that one. I’m not the kind of person who has illusions about American innocence, but it is the American style to reinvent, to renew optimism, and that is often confused with patriotism. Patriotism, for me, invokes conflicting feelings. So many patriots are really rascals — you know, last refuge of the scoundrel — nationality is a dangerous thing. But I believe in the ability of man and woman to overcome.”

His primary concern is the “easy militarism” that seems to be some kind of default condition of the American mind. However much that view is undermined by movies like his, the pendulum swings back. “If you look at the late 1990s, when America was prospering so much economically, we drifted back into that easy militarism again — you look at all the invasions that happened from 1989. Even the day Born on the Fourth of July came out, we invaded Panama. It killed our business ...

“Then there was Private Ryan — a wonderful film, but promoting the concept of the greatest generation — and then that gave way to this shock and awe. I mean, I loved Black Hawk Down, but they must have made that film with Pentagon approval, they couldn’t have got those helicopters... Although the film was about losing, the men were so perfectly trained, they were robotic in battle. The cartoonish thing keeps coming back, then we actually go to war. Black Hawk Down was a precursor to Iraq 2. It was as if the merger between entertainment and war had been achieved at last.”