This lightly comic portrait of Tourette syndrome campaigner John Davidson is driven by an impressive central performance. In the late 1980s, John Davidson became something of a household name in the UK as the focus of a profile documentary on BBC television. John’s Not Mad offered a window on the life of a Galashiels teen with Tourette syndrome, and it encompassed a pathfinding social push to educate the public on a condition about which little was known. Indeed, during his early life, John was chalked up as a mouthy, self-destructive reprobate as he had no way to convince his family and peers that his jerking tics and bursts of florid invective were, in fact, impulsive rather than controlled.In Kirk Jones’ breezy, sentimental film biog of Davidson, his inclusion in that BBC doc and the subsequent minor celebrity he enjoyed are bypassed in favour milking drama from the subject’s outsider status. Scene after scene plays out in a similar mode, with John being momentarily empowered to try something “normal” and then it all goes spectacularly wrong. It makes for quite stressful viewing, as in many of the situations you’re watching through metaphorically clasped fingers just waiting for the ball to drop. Trips to the shop, a night in the club, and even a spell as an, ahem, local courier for some unsavoury types, all quickly go south, as Jones puts most of his chips on John’s (and, by extension, other people with Tourette's) inability to conform socially. What the film does have going for it is a remarkable and charismatic performance from actor Robert Aramayo (best known for a minor role as a young Ned Stark on Game of Thrones), who has not only gone to great lengths to build an uncanny physical resemblance to the real Davidson, but also displays a sublime mastery of his body in actually appropriating the splenetic physical motions of the condition. In this version of the story, Davidson is presented as a happy-go-lucky chancer with a largely optimistic outlook – he does his best to reject a future of total exclusion and lives in hope that everyone has their little nook in the end, which the film cheerly confirms.Among the supporting cast are a host of British greats: Shirley Henderson as John’s long-suffering single mother who made the difficult decision of rejecting John to preserve her own mental health; Maxine Peake as the indefatigable mother of one of John’s pals whose suffering from terminal cancer; and then Peter Mullan, the salty caretaker of a community centre who sees John’s true potential and hires him for his first proper job. All do their best in what feel like not-massively-challenging roles.The film cleaves closely to convention, and artificially ramps up heart-pounding with its many on-the-nose musical selections and emotive longueurs. The final chapter charts John’s evolution into a celebrated Tourette’s activist, as well as his inclusion in medical trials to help tamp down the effects of the condition. It’s well meaning and all done with the best of intentions, but it doesn’t really say or do much more than the BBC documentary did nearly 40 years ago. The post I Swear review – a well-meaning, overly sentimental biog first appeared on Little White Lies.