Creating a Cannes scene

On the arousal front, those who made it past the men in blue are likely to have been disappointed: Reygadas's film is a slow, carefully composed meditation on issues that could hardly be further from the gynaecological realism of porn.

Like the director's syntax, the film is at times impenetrable. Its main plot point - the kidnapping of a child by Marcos and his wife which ends in the child's death - has happened by the time the film starts.

"It's not important," insists Reygadas. "The only important thing is that it happened. From then on, Marcos will be suffering from this act which causes irreversible damage." The hapless chauffeur subsequently consolidates the damage with another, equally shocking act of violence before joining a pilgrimage and ending up dead in a basilica.

I suggest that this might be seen as redemption but, as usual, this is too straightforward a reading for Reygadas. "No, no, you are wrong," he says, sighing patiently. "Let me explain. It's not that he's redeeming himself. He realises that the only decent thing he could have is death. Spending the rest of his life in jail is just a way of redeeming himself in the eyes of hypocritical society. He goes and looks for death and he is granted his wish."

Where, then, does that leave the Battle in Heaven of Reygadas's title? "I prefer evocative titles which may evoke a feeling that you can complete with your own thoughts. My title could evoke Olympus - the gods fighting over the destiny of people on earth. Or it could evoke the battle Marcos is having on earth in Mexico City which, ironically, could be called heaven. It's open."

Reygadas used non-professional actors for his film. Ana is played by Anapola Mushkadiz, who comes from a well-off Mexico City family, and a real-life chauffeur, Marcos Hernández, makes his debut as Marcos.

Reygadas had known Hernández for years, but Mushkadiz came out of "a traditional casting, although it wasn't so traditional because I said 'No actresses, please!'"

To hear Reygadas tell it, the couple breezed through the sex scenes like ... well, like pros. "It was very easy," he says airily. "They just got naked and did what I said. There was a little embarrassment, maybe in the first 10 minutes. But after that, they were walking naked around the studio for the whole day."

The film is also, Reygadas insists, about his native country, represented by the opening scene proper (the blowjob comes pre-credits): a sequence in which Marcos acts as a kind of security guard to an extraordinary (but apparently real) daily raising and lowering of an enormous Mexican flag in the centre of the city.

"In Mexico," says Reygadas, "we are not frightened of the army, like they are in other Latin American countries. Sure, corruption and petty crime happen all the time but there's not structure, so we have this need for organisation. I think that is what is really indecent at the beginning of the film: all this business with the flag, not two people having sex."

Now that Battle in Heaven has been unleashed on Canne s, Reyg adas, insists that he has finished with it. "I really feel when I finish a film that it is not mine any more," he claims. "You give it away. It's like you give a present because you want to. You expect people to like it. You want them to put it in the middle of the living room. But if they put it away in a drawer, well, that's it."

The critical response has been as polarised as any I can remember in 23 years of covering the festival, with the booers appearing to outnumber the clappers. But the response at the official competition screening later in the day saw none of the expected walkouts, and ended with a five-minute standing ovation.

Some dismiss Battle in Heaven as an empty exercise in pretension. Others see it as a great leap forward from Reygadas's earlier arthouse hit, Japón, and a strong contender for Saturday's Palme d'Or.

And Reygadas? "I made it out of love," he says with surprising clarity.