EVERYBODY loves a good underdog story – which might explain how the ill-fated amateur round-the-world sailor Donald Crowhurst got as far as he did in the first place.

That and the British dreamer-in-a-cardigan’s sheer bravado.

Crowhurst convinced a bunch of hard-nosed businessmen to back his 1968 attempt to single-handedly circumnavigate the globe even though his business was struggling and he had extremely limited experience in open water.

By the time Crowhurst was forced to admit that his plan to build a 12 metre trimaran to compete in The Sunday Times-sponsored race was too ambitious, he had backed himself into a corner.

Director James Marsh, whose career spans documentaries and features, is perhaps uniquely qualified to tell Crowhurst’s story.

Colin Firth’s assured, understated performance as the contemporary Don Quixote keeps the biopic on an even keel.

The Mercy, which takes its title from a line in Crowhurst’s log book, also draws attention to the part the media played in his downfall.

Turning back means public humiliation and financial ruin.