Ajunior football team trapped deep inside a flooded cave in Thailand are making headlines all over the world. Not even the Thai Navy Seals have been able to save them and their chances of survival are bleak. That is, until a pair of middle-aged Britons arrive on the scene. Rick and John don’t exactly look like action heroes; one is bald, the other bespectacled, and both could be described as bumbling. But they are two of the world’s best cave divers, and in 2018 they led one of the most dramatic rescue missions of recent times. This hugely involving documentary from Elizabeth Chai Vasarhelyi and Jimmy Chin, the directing duo and married couple behind the Oscar-winning climbing documentary Free Solo, centres on the rescuers rather than the rescued (the rights to the boys’ story were speedily bought for another project, by Netflix). Twenty-four-hour news coverage of the event is integrated seamlessly with footage filmed by locals and reconstructions starring the divers themselves. Vasarhelyi and Chin recreate the sense of the clock running down as oxygen levels in the cave decrease, while the monsoon outside rages. But the dilemma at the heart of the film is ethical as well as practical; once the boys have been located and found alive, the divers still have to get them out. The plan involves sedation, with Australian diver and anaesthetist Harry comparing the process to euthanasia. The stakes feel enormous as these hobbyists are suddenly shouldered with such responsibility – to pull off a group effort on the world’s stage.