When Robert De Niro appears at the Karlovy Vary festival with his family in tow he seems a changed man. Gone are the legendary monosyllabic replies and tight-faced grimaces, replaced by an easy smile and a twinkle of the eye.

The festival, whose organisers are honouring the star with a retrospective and a career achievement gong, takes place in a spa town two hours drive from Prague. Karlovy Vary is the antithesis of glitzy events such as Cannes and Venice. Students invade the sedate environs, camping out under the stars or sleeping in school gymnasia to overdose on films for ten days.

This relaxed atmosphere could account for De Niro’s chilled demeanour. He is accompanied by his wife of 11 years, Grace, son Elliot, 10, and his 13-year-old twin sons, Julian and Aaron, the products of his relationship with ex-model and actress Toukie Smith.

Woody Allen once said he and De Niro both knew how to make people keep a respectful distance: ‘You move fast and keep your head down. People don’t bother you when you’re busy.’ But here De Niro happily signs autographs for the crowds. So how did he acquire his reputation as a ‘difficult’ actor? He mulls over the question before answering: ‘You can have integrity and not necessarily be difficult. As a director I don’t like it when an actor is temperamental. When you do a movie everyone should leave personal problems at home. It’s difficult enough to make a movie as it is ‐ you don’t need any extra drama to get it into the can. You just need to show up, speak your lines, earn your pay-cheque and leave the ego behind.’

Despite such deprecation of his art, De Niro frequently contributes more than these basics. Indeed, he co-produced his latest film What Just Happened?, a Hollywood satire directed by Barry Levinson. The film, which stars De Niro as an ageing producer trying to save his career, opened at the Sundance Film Festival in January, then was selected as the closing film at Cannes and Karlovy Vary. By Hollywood standards its budget is low, coming in at a cool $25 million, but manages to secure some amusing cameos from Sean Penn and Bruce Willis.

Yet, for all its pedigree, What Just Happened? was critically mauled and struggled to find a distributor in Europe. De Niro is quick to defend the film: ‘In retrospect I don’t think there are any bits we could take out or reconfigure. Barry [Levinson] was trying to work out certain things and it was always a kind of work in progress.’

So, is Hollywood really as ruthless as it is portrayed in Levinson’s satire? ‘It’s just like any other business,’ says the actor. ‘But it’s more visible because it’s Hollywood. People do what they have to do.’

De Niro returns to more familiar hard-boiled territory opposite Al Pacino in the forthcoming police crime thriller Righteous Kill. He and Pacino previously worked together on 1995’s Heat. The pair play veteran New York detectives working to identify a possible connection between a recent murder and a case they believe they solved years ago. The new thriller was a project De Niro pushed to get made. ‘In Heat, we only had one scene together, which is my favourite scene in the movie; I thought it was well written and a great scene to watch, so I wanted to build on that,’ he says.

Away from making movies, De Niro set up his own Tribeca Film Festival as part of a plan to regenerate New York’s post 9/11 downtown area. It has rapidly acquired a reputation as a serious and exciting date on the crowded calendar.

‘I left a meeting right after they hit the World Trade Center,’ he says. ‘I went to my apartment and I watched it out of my window. I could see the line of fire across the North Tower. I had my binoculars and a video camera ‐ though I didn’t want to video it. I saw a few people jump. Then I saw the South Tower go. It was so unreal, I had to confirm it by immediately looking at the television screen. That was the only way to make it real. Like my son said, “It was like watching the moon fall”.’

The actor recently decided to quit his long-time agency, Creative Artists (CAA), which resulted in a vindictive email from one of the staff, berating De Niro for having too high an opinion of his own worth and being ungrateful for the roles CAA had put his way. The email also suggested that De Niro was over the hill as far as the younger generation of filmgoers was concerned. Rather than getting shirty, he says of this incident: ‘There are certain facts about it that are just inaccurate. I hate to think the email came from someone at CAA, because I felt it was beneath them. It’s like an obscene telephone call. You just don’t know where it comes from.’

Inevitably, De Niro frequently gets asked about the earlier part of his career, particularly his enduring collaboration with director Martin Scorsese on films such as Mean Streets, Taxi Driver, Raging Bull and Goodfellas. The actor claims he never felt rejected when he started out as a jobbing actor desperate for work. ‘When you go into an audition, you’re rejected already. There are hundreds of other actors. At this point in my career, I don’t have to deal with audition rejections, so I get my rejection from other things. My children can make me feel rejected. They can humble you pretty quick.’

De Niro is also fairly sanguine about his famed Method preparations, which included gaining 60 lbs and learning to box for his role as Jake La Motta in Raging Bull.

‘I spent lunchtime in a grave during the filming of Bloody Mama,’ he says. ‘When you’re younger, you feel that’s what you need to do to help you stay in character. When you get older, you become more confident, and less intense about it ‐ and you can achieve the same effect. When you’re relaxed and confident, you get the good stuff.’

He relishes the new horizons that have opened up to him on the other side of the camera. ‘I like directing. With The Good Shepherd it took me years to get things going. I started nine or ten years ago and it really took that long to get it going. I’d like to do a ‘next episode’ of The Good Shepherd, which goes from 1961 with the Berlin Wall going up to 1989 with the Wall coming down. Then I’d like to do a third film from 1989 to the present.’

He would love to work with Scorsese again and the pair have a couple of projects under wraps. ‘We’ve done eight movies together and I’d like to do another couple with him. We’re going to do this project in a year or two. I’m superstitious about talking about it, but it’s supposed to be happening. Marty’s open to unexpected things on that ‐ this is a flowery way of saying it ‐ on that voyage. He takes ideas, and he’s not afraid to try them.’

Righteous Kill is out on Fri 26 Sep; What Just Happened? is out on Fri 10 Oct.