Timothy Spall is perfect as JMW Turner in director Mike Leigh’s magnificent biopic, which depicts the 19th-century painter in the last 25 years of his life.

Earthy, boorish, single-mindedly devoted to his art, Spall’s Turner grunts and growls, gurgles and wheezes, but the performance could not be more eloquent, revealing the artist in all his contradictions and genius. And Leigh’s is an astonishing achievement, too, daringly upending the timid conventions of most period biopics to create a compelling and convincing cinematic portrait.

And, when Turner upstages his fellow artists on varnishing day at the Royal Academy, brazenly daubing a blob of fresh red paint on his seascape canvas, it’s easy to detect shades of the director’s own audacious confidence.