The Mercy (Cert 12, 110 mins, StudioCanal, Drama/Romance, available from June 4 on Amazon Video/BT TV Store/iTunes/Sky Store/TalkTalk TV Store and other download and streaming services, also available from June 4 on DVD £19.99/Blu-ray £24.99)

Starring: Colin Firth, Rachel Weisz, Ken Stott, Eleanor Stagg, Kit Connor, Finn Elliot, David Thewlis, Jonathan Bailey, Simon McBurney.

Amateur yachtsman Donald Crowhurst (Colin Firth) attends a 1968 trade show with his sons Roger (Kit Connor) and James (Finn Elliot) to sell their invention: a nautical navigation device.

The family's pitch is interrupted by a rousing speech from pioneering sailor Sir Francis Chichester (Simon McBurney), to launch the Golden Globe Race, which promises a £5,000 prize for the first sailor to single-handedly navigate the world non-stop.

Donald has always been a dreamer and he informs his wife Clare (Rachel Weisz) that he intends to take up the mantle.

Buoyed by investment from local businessman Stanley Best (Ken Stott), Donald begins construction of a revolutionary triple-hulled yacht christened the Teignmouth Electron.

Media publicist Rodney Hallworth (David Thewlis) and assistant Wheeler (Jonathan Bailey) are drawn to Donald's underdog story, attempting the impossible against seasoned sailors like Robin Knox-Johnston.

The Mercy is a handsome but emotionally waterlogged dramatisation of Crowhurst's fateful journey of self-discovery, directed by James Marsh, who captained The Theory Of Everything to Bafta and Oscar glory.

Romance bubbles to the surface of Scott Z Burns's script but there are noticeable leaks when it comes to visualising the deterioration of Crowhurst's mental state in the claustrophobic confines of the yacht.

Firth delivers a committed performance while Weisz is stranded on dry land and off screen for extended periods, so she fails to make a significant impact.

A ramshackle script bobs between present and past, inserting flashbacks to happier times in Donald and Clare's relationship as his sanity unravels.

Rating: **