Just last month, we had a new movie entitled The Mercy, starring Colin Firth, about the strange true story of amateur British yachtsman Donald Crowhurst who entered a round-the-world sailing competition in 1968, started radioing in fake coordinates when the going got rough and finally took his own life at sea, overwhelmed with loneliness and guilt.

That wasn’t a bad film, by any means, but here is a second one on exactly the same subject, from the indie horror director Simon Rumley. It is frankly superior in every way. By getting inside Crowhurst’s head, and giving a nightmarish, impressionistic account of what he finds there, Rumley really nails Crowhurst’s naive ambition and his terrible fear. With long, detailed wordless sequences, he solves the problem of how to portray Crowhurst’s solitary existence on the boat – all of this in a way that The Mercy never came anywhere near.

The details are tremendous – the baked beans, the toothpaste, the little foot pump that squirts freshwater into his kettle. It looks very much like the caravanning holiday from hell, and casts a weirdly convincing new light into why a caravan entrepreneur should want to sponsor Crowhurst in the way that he did.

Justin Salinger is absolutely superb in the lead role, heartwrenchingly convincing as the decent British chap who wears pyjamas as he goes to bed on board his boat every night: thin, clenched, wiry, doggedly making the best of it. Salinger exposes how miscast Firth actually was in the role, honest and heartfelt though Firth’s performance was. With a lower budget but a much fiercer, and more intuitive grasp of the material, Rumley has made a tremendously good and moving film.