The reason for his outrage? A little film that had a big impact two years ago. La Haine (Hate), which Kassovitz wrote and directed, traced 24 hours in the lives of three Parisian youths trying to relieve the tedium of life on a riot-ravaged housing estate. This was a side of France that film-makers had largely shunned, and reaction to the picture was split between those who were relieved that someone had dared to lift the lid off this boiling pot, and others who recoiled from its merciless heat. La Haine proved to be an unprecedented box-office hit both at home and abroad, its success fuelled by the controversy whipped up by the French media, who were as appalled as my cabbie to note that Kassovitz himself was a middle-class boy from the right side of the tracks - the wrong place to be born if you want to comment on poverty without attracting flak.
Kassovitz went on to win two Cesar awards, as well as the Best Director prize at the 1995 Cannes Film Festival. It is true that around this time he thought he was a god, though it's hard to reconcile such arrogant bluster with the polite, mousy little man seated before me in a baseball cap and cricket sweater, who becomes most animated when talking not about politics, but about his passion for American Graffiti and Monty Python and the Holy Grail, two films whose scripts he can recite backwards. Nobody was more appalled at the transformation from movie-nerd to megaphone-wielding, stimulant-ingesting megalomaniac than Kassovitz himself.
"I don't like awards because it's a nasty idea," he explains. "The competitive aspect is bullshit." Coming from somebody who has won three awards each for his acting and directing accomplishments and still has yet to reach his 30th birthday, this might sound like cheap talk. But Kassovitz speaks from experience.
"I've always hated competition. It's not about how happy you are. It's about how unhappy the other guy is. It was a pleasure to win at Cannes for La Haine, and it did a lot of things for me and my pay cheque. But it did a lot of wrong to my head. When you have the Best Director prize, you start thinking: `Hey man, fuck you, fuck the rest. I'm the best.' Then you begin spending all your time in clubs and it stops being about film because you don't have to work, and then you go on a film set again and realise you're not Coppola. That's what happened to me. I thought I was a good director. Then I realised I'd been living off what other people thought of me."
While he was struggling to keep his ego in check, Kassovitz found that La Haine had unexpectedly made him the media's prime target. By the time the French government had ordered a screening of the movie in order to discern whether or not its frank portrayal of life on the breadline was going to precipitate the end of civilisation, Kassovitz's personal life was being dragged on to the front pages - hence the taxi drivers of Paris possessing intimate knowledge of everything but his bank balance.
Did he realise the effect that the film would have on his life? "No! It was a small black-and-white movie - I had no idea it would cause so much fuss. The first day of its release in France, the theatres were full. We had five newspaper covers, four magazine covers. It was a national event. Not because of the quality of the film, but because the media in this country are lazy and stupid. They did a lot of good for the film because more people went to see it, but they totally misrepresented it. They were more interested in saying to me, `You're not from the ghetto. So why are you making films about ghetto life?' That's sad. After a while I started thinking that we shouldn't have made the movie. I had problems out in the street with guys from the ghetto - they said I had betrayed them and then I couldn't even say `Hey, fuck you!' to them because I began to believe that I had sold out. The trouble is that if you want publicity, you have to face the media - and the media have a tendency to... exaggerate."
Kassovitz has just finished directing and acting in a new film which he tells me concerns misrepresentation-by-media - Assassins, based on his own 1992 short - and is currently on let's-do-lunch terms with Jodie Foster's Egg Pictures company, who will be behind his first English language film. But before either of those projects are released, we have a chance to see him step before the camera in Jacques Audiard's fiercely intelligent comedy-drama A Self-Made Hero, in which Kassovitz plays Albert, an inconsequential sideliner who muscles himself centre-stage by inventing a past for himself as a Resistance hero.
As the film unfolds, the Second World War is drawing to a close, but Albert's new, brighter life is just beginning, and Kassovitz delicately captures the way this timid young man is invigorated and emboldened by the lies which he disguises as history. Although A Self-Made Hero is light years away from the style and tone of La Haine, it too concerns itself with raising topics that many in France would rather remained unmentioned.
"French people talking about the French Resistance in an honest way is really something you don't hear very often," Kassovitz says. "When I was a kid, we were taught that everyone in our country was good. It's only when you grow up that you realise how anarchic that post-war period was, and how nothing was clearly defined.
"Today we have teenagers who dress like gangsters, and who knows if they're rich kids or poor kids? Nobody looks like who they really are. At that time it was the same. But it wasn't about music or fashion. It was about rebuilding society after the war. Telling lies is part of human nature, but can you do it as a politician? Can you lie for a good cause? If you do, then you have to be true to your lie. That's what I like about Albert. He acts like a member of the Resistance and he's actually very good. If he'd had the chance to be in the Resistance, he might have been a real asset."
These days, Kassovitz talks about his achievements with a humility that could charm a disgruntled Parisian taxi-driver, almost as though he is repenting for his former egotistical excesses. He is particularly modest about acting - he maintains that he starred in his own first feature, Metisse, only because it was easier that way, and naturally neglects to mention that the performance won him Most Promising Young Actor trophies from cities where you wouldn't even think they had film festivals.
"A director is what I am," he says. "Acting is what I do to help me learn to be a good director. You get money, comfort, girls. But it's not that creative. I consider it a hobby that I use for my real job. Actors are the most important thing in a film, so it's healthy for me as a director to know what they go through. But I've never read a book about acting. I don't have a technique. I say to a director: `I don't know if I can do this. If you believe in me and want me for your film, that's your responsibility but maybe I'm not going to be that good' "
`A Self-Made Hero' opens on 4 April