Based on the incredible but all too true story of amateur sailor Donald Crowhurst's solo attempt to circumnavigate the globe, The Mercy is the new film from The Theory of Everything and Man On Wire director James Marsh.

Starring Colin Firth as the man himself and Rachel Weisz as his long-suffering wife Clare, the film offers a deeply touching retelling of the events which led to one of the saddest stories in the history of modern competitive sailing.

The year is 1968 and Donald Crowhust (Colin Firth) is preparing for the voyage of a lifetime. Spurred on by a wave of enthusiasm for the sport and the prospect of a handsome win, Crowhurst embarks on a project which could see him circumnavigating the globe alone in the hope of winning the very first Golden Globe Race.

As the departure day approaches, Crowhurst begins to have doubts about his own abilities as a sailer and starts to wonder whether he should go through with it.

Not wishing to let his financial backers or his own enthusiastic children down, the hapless sailor has to bite the bullet and pretend that he can still be in with a chance despite knowing almost nothing about the sport. However, things start to go pear-shaped when Crowhurst finds himself trailing behind everyone, and decides to lie about his whereabouts, which soon puts him ahead of some of the most seasoned competitors.

 Firth does a truly impressive job in depicting Crowhurst as a timid everyman seduced by the desire to be someone else. He offers the sailor as a man broken by his own actions and bewildered by the events taking place around him, while Weisz puts in a commendable turn as the dutiful Clare despite being given very little to work by a screenplay which is slightly lacking in places.

However, it is David Thewlis as Crowhurst’s no-nonsense northern press agent, Rodney Hallworth, who steals almost every single scene he’s in. His blunt and concise manner manages to rise frequent smiles and guffaws, which if one is to be completely honest, is a welcome distraction from the doom and gloom taking place on screen.

On the whole, March and Writer Scott Z. Burns offer a fairly conventional narrative held together with some commendable period set pieces and some very strong performances courtesy of Firth et al.  All in all, a perfectly well told story, which could have benefited from a stronger hook and perhaps a more believable female protagonist.