We are living through a mini-boom in documentaries about North Korea. Film-makers are getting into Pyongyang to shoot – clandestinely, semi-clandestinely and on various pretexts – those vast statues and eerie cityscapes. Werner Herzog’s Into the Inferno suggested the North Koreans’ defensive mindset had something to do with living in the shadow of a volcano, Mount Paektu. Norwegian director Morten Traavik told the extraordinary story of how obscure Slovenian art-rockers Laibach became the first Western band to play North Korea. Alvaro Longorio’s The Propaganda Game argued that North Korea is a zombie state, kept alive by the duplicitous interests of great powers, and Ross Adam and Robert Cannon’s The Lovers and the Despot is about the staggering true story of how in late 70s the movie-mad North Korean leader Kim Jong-il actually kidnapped a South Korean director Shin Sang-ok and his wife Choi Eun-hee, and forced them to work in his industry.

Now the legendary documentarian Claude Lanzmann has entered the field with this flawed, self-indulgent but still fascinating effort, basically a single-ancedote testimony about his own incredible experience in North Korea in the late 1950s: a brief-encounter-style love story with a North Korean Red Cross nurse. It is in fact a story that he included in his 2012 memoir The Patagonian Hare, but certainly bears repeating.

Lanzmann is a film-maker with a genuine connection with North Korea, who has some expertise in the subject, and so is different from the various wide-eyed film-makers who have found themselves there; although in his location work around Pyongyang, he experiences the same old thing as everyone else: the smilingly oppressive guides who pluck at his sleeve and try to stop him filming where and how he wants.

The movie begins with Lanzmann giving a brief historical sketch of the Korean war and the fact that the US used napalm against the communist North; he tours around Pyongyang, where he appears to have been given permission to film on the grounds that he is making a movie about martial arts and Taekwondo, and there are some very entertaining setpiece scenes of the North Korean fighters strutting their stuff. He is given a tour of the ruling party’s collection of weapons captured from the Americans and British during the war, and Lanzmann rather outrageously flirts with the female army officer who is his guide. All these things will find an echo with the story he has to tell. And basically the entire second half of the film is taken up with a closeup on his face in various contexts, in Pyongyang and at home in Paris, as he tells it.

In the late 1950s, Lanzmann was a part of a leftist cultural delegation to North Korea, and feeling unwell one day, he asked if he could be given some vitamin injections. These were performed in his hotel room by an exquisitely beautiful Red Cross nurse, Kim Kum-sun, whom he ended up kissing passionately and he had a romantic but chaotic boating trip with her in the city. Their affair was unconsummated, but it reaches an eroticised climax – which Lanzmann has clearly perfected in the repeated retelling over the years – in her partly undressing and revealing a personal scar which explains the title. But they were parted after a scary encounter with the authorities which Lanzmann was evidently able to brazen out, due to his VIP status.

So does Lanzmann make any attempt to find her now, in 2017? No. He says it is because he does not care to see the effects of age and time: a very ungallant attitude, surely, and anticlimactic. His monologue is not edited, so as to disperse it into a larger documentary framework; he doesn’t get to tour around with his camera, attempting to provide any sort of context to his story. He just gives us his long continuous testimony whose subject matter might seem a bit sensationalist and facile, compared to those in his great work, Shoah, about the Holocaust.

And yet, and yet. It really is a gripping story, at least partly for what Lanzmann leaves out and a possibility he does not wish to acknowledge. If this story was happening in a novel written by, say, John Le Carre or indeed Frederick Forsyth, we would not be taking Kim Kum-sun at face value. Could she have been, if not a honeytrap exactly, then someone who had informed the authorities what was going on? Could she, in some indirect way have been pressured and coerced into spying on Lanzmann? The thought can’t be dismissed: and the fact that he appeared to be able to halt the informal “tribunal” into her misdemeanours, and that she was able to write to Lanzmann later, referring affectionately to their boating trip, all indicate that there was something going on. But who knows?

Napalm is indulgent, certainly. It doesn’t stop it being a gripping story.