Christopher Martin’s film is an urgent documentary version of Under the Wire, the memoir published by war photographer Paul Conroy about his friendship and professional partnership with the Sunday Times correspondent Marie Colvin, and their terrifying experience together reporting from the killing fields of Syria in 2012, when the Assad regime was brutally slaughtering civilians. Colvin was killed, along with fellow journalist Rémi Ochlik. (A character in Eva Husson’s movie Girls of the Sun, which premiered at Cannes, was inspired by Colvin, who had lost an eye while reporting from an earlier war zone and wore an eyepatch. She was perhaps not displeased with her own celebrity and brand identity, although this film shows that she found it prudent not to wear the eyepatch in Syria. Drawing attention to yourself wasn’t safe.)

Conroy is a terrific interviewee: smart, funny, unsentimental and a great raconteur. His talking-head moments work very well with the terrifying footage he shot. As ever with war journalism, the objection is that it creates an undifferentiated, apolitical spectacle of horror in which only the names of the countries and cities change, and I sometimes felt myself growing restive. But Conroy’s argument is that we have to bear witness to human suffering, that this will always be valid, because this suffering is always in danger of being covered up by politicians. And after Colvin’s death, the ordeal for Conroy and other journalists with them in Syria was only just beginning. This is a heart-stoppingly suspenseful story. Conroy is a superb commentator on war and all its cruelties and absurdities. Maybe he should be giving us words as well as pictures on a regular basis from now on.