He said he was making a film about taekwondo. But the great French director was actually on the trail of an old flame he had a secret romance with in the 1950s

At 91, Claude Lanzmann is a virtual folk memory of cinema. He is the former teenage fighter in the French resistance whose Jewish family went into hiding when war broke out. In 1985, he directed Shoah, the eight-hour documentary about the Holocaust composed almost entirely of first-person testimony. Now in Cannes, he has premiered a film about his personal experiences in North Korea. Napalm is a movie that, initially, takes its cue from the underreported fact that the US used the incendiary weapon in the Korean war of 1950-53.

Napalm review – Claude Lanzmann's gripping account of erotic encounter in North Korea Read more

Last year, Lanzmann bluffed his way into North Korea on the bizarre pretext of making a film about the country’s love of taekwondo, and indeed his documentary does contain hilarious footage of terrifying fighters. But Lanzmann had another purpose: he wanted to revisit the place in Pyongyang where, in the 1950s, he had an extraordinary experience.

Visiting as part of a cultural delegation, Lanzmann felt unwell one day and asked for vitamin injections. These were administered by a beautiful nurse called Kim Kum-sun , who made daily visits to his hotel room and with whom he ended up having a passionate romance – until they were discovered by the authorities.

The second half of the film is given over to his first-person account. It is a story that is political, personal, erotic and sad. Lanzmann spoke to me about the experience in a villa on the Croisette. He is a solid, Buddha-like man, sometimes resting his chin on his cane, gazing impassively out to sea as he considers my questions.

Facebook Twitter Pinterest Statues of late leaders in Pyongyang, captured in Napalm. Photograph: Cannes film festival

How did he approach such a personally painful subject? “It was a challenge to make a film with a story from my own life. Another man might have said, ‘OK, we will shoot this film as fiction. It will be in another country, in Asia, yes, but another country, another river – and with actors.’ But no, this story happened to me. It would be difficult to give my part to just anyone, to an actor. It would be a betrayal.”

What about the difficulties of shooting in North Korea? “It was almost impossible. There were always people there holding me – very strongly.” He grabs his right forearm to show me. “Sometimes they put me in pain. But I couldn’t say what I was doing. They thought I was making a film about taekwondo.”

Lanzmann giggles at the absurdity. But those scenes allowed him to get around in Pyongyang, although always harassed by his official minders with their strange fixed grins. “Those scenes about taekwondo are very funny,” he laughs. “But then we get to the main story, about me. I am now old and wrinkled, and did the best I could.”

It is a tremendous tale. But how about an ending? Was he tempted to try to contact the nurse? Lanzmann’s reply is emphatic, even curt: “Non. No. I did not want. She is probably dead. Life is shorter there than here. But even if she is alive, to see her as an old woman, I did not like this idea.” I thought, on watching the film, that there was something incurious, even ungallant, about Lanzmann’s reluctance. But now I can see his pain at the thought. It would have been a kind of taboo.

Facebook Twitter Pinterest ‘Life is shorter there than here’ … Lanzmann in Napalm. Photograph: Cannes film festival

But could this nurse have been some sort of honeytrap, someone who knew more than she was letting on, and had some complicity with the authorities? Again, Lanzmann’s response is cutting: “It is impossible. When we started to … to … embrace” – he mimes hugging – “and kiss each other madly, there was no preparation. It would be impossible. It is probably because you read too much John le Carré that you think this. But I like your idea. It is a very British idea.”

Like any film-maker who has been in North Korea, he is fascinated by Pyongyang, an extraordinary place, a final frontier of strangeness. “It is like a dream. It is a city that is monumental. And empty. It is a city of ‘as if’. When I was there in the 50s, you could see a policewoman with Soviet uniform and cap, directing traffic at the corner of the street, mechanically. It was funny because the traffic was only pedestrians. There were no cars.”

Does he think North Korea will be the site of a new Cuban-missile-type crisis with Donald J Trump? “I cannot think this. There is a lot of bluff. They are very, very far from being able to launch a missile at the US. They play with this, they are clever. But you know, the North Koreans will become the best friend of Trump. It is not impossible. Trump is a very funny bloke.”

Perhaps he should make a film about the US president? Lanzmann nods and smiles. “Yes, it is possible. If I do this, I will call you.”