This very picturesque documentary opens with celebrations and ends in desolation - but a looming sense of doom can be felt right from its start. "A classic tale of English daring-do on a shoestring", it tells the story of the 1968 Sunday Times Golden Globe sailing race, the event which led to the first ever single-handed non-stop circumnavigation of the globe. The directors Louise Osmond and Jerry Rothwell choose not to focus on the eventual champion Robin Knox-Johnston, but on another competitor - the relatively inexperienced amateur sailor Donald Crowhurst - who had staked his house and his financial security on the outcome of the race. Mere hours off shore and Crowhurst was already in trouble, his prized boat leaking. The film tells the story of his increasingly desperate voyage. Balancing interviews with footage of the implacable ocean taken by Crowhurst on his 16mm camera, Osmond and Rothwell carry their tale to heart-rending heights. Securing Tilda Swinton's measured narration - her voice so familiar to us from Derek Jarman's poetic tragedies - was another real coup. It makes the gut-punch of a coda, when it comes, hurt just that little bit more. Most resonantly of all, this is a film charged on the dangers of imagination. In that sense, it reminded me of this year's landmark documentary, Ari Folman's Waltz with Bashir. Both are hauntingly incisive yet deeply compassionate studies of masculinity pushed to its limits - with no direction home.