The controversy sparked by John Davidson – the subject of this film – and his involuntary shouting of racially offensive language at the recent BAFTA Awards, at which he was a guest, has generated much discussion on the limits of tolerance and also opened a window onto the complexities of life for those living with Tourette syndrome. It is into this fraught terrain that I Swear steps.

Robert Aramayo in I Swear

Written, directed and co-produced by Kirk Jones (Waking Ned, Nanny McPhee), I Swear takes us to Scotland in the early 1980s to tell Davidson’s story, that of a Galashiels boy (played by Scott Ellis Watson at first) who develops Tourette’s – the neurological condition that results in a spectrum of physical tics, compulsive behaviours and uncontrollable (sometimes obscene) shouts – as a teenager.

Ostracised at school, John’s vocal tics make him a figure of fun to some, an easy target to others. His family is variously aghast, ashamed and disappointed. His dad (Steven Cree), who nursed hopes that John might become a professional footballer, leaves, never to return. At the very point when a young man should...