He was the man, you might remember, who vanished overboard in 1969 after mentally unravelling at sea during the first nonstop race around the world – a race he was catastrophically ill-prepared to take part in. He left behind a grieving wife and four young children.

In The Mercy, Colin Firth offers us a more generous view of Crowhurst; it’s an attempt, you sense, to rehabilitate the reputation of a man history hasn’t treated too kindly. To recap, not just did he abandon his family for an impossible sailing challenge, but when he realised neither he nor his boat were fit for purpose, he began fabricating his position in the race. In this, he was aided and abetted by his PR man back in England, former Daily Mail crime reporter Rodney Hallworth, brilliantly played by the scene-stealing David Thewlis.

Crowhurst is portrayed as neither a fool nor as someone who is consciously reckless. Rather he is the victim of a fermenting craving not just to make his mark on the world, but also to please those closest to him – a fantasist rather than a fatalist, an inexperienced gambler who naively twists rather than sticks when the cards are against him.

Firth’s characterisation pitches from that of the affable optimistic onshore (you might just get a sense of Richard Briers’s character in TV’s The Good Life) to tormented and desperately unstable after six months of solitude at sea, much of it spent going around in circles in the south Atlantic.

It’s an uncomfortable study of a man who realises he’s about to lose everything. “I can’t go on. And I can’t go home. So where else is there?” he laments. James Marsh (director of documentary Man on Wire and the Stephen Hawking biopic The Theory of Everything) helps draw superbly nuanced performances from Rachel Weisz, who plays Crowhurst’s supportive wife Clare, and Ken Stott as the businessman who funds the sailor’s dream but whose penalty clause means that Crowhurst forfeits his house and business if he doesn’t finish the race.

The Mercy is a powerful and compelling story told with care and compassion by a brilliant cast. Whether Crowhurst deserves that compassion might divide audiences. But Marsh’s film invites us not to judge Crowhurst but to judge ourselves. What would we do in those same circumstances?

The Mercy is released in cinemas on Friday 9 February