Mike leigh’s film about J.M.W. Turner is not, he emphasises, a biopic. There’s no dalliance with the artist as Covent Garden-born prodigy. Instead, we catch up with him well established in the art world in the 1820s, aged 50, with a house in Marylebone where a dedicated housekeeper, Hannah Danby, prepares his canvases and pigments, a task she had carried out for 40 years by the time of Turner’s death in 1851. By starting into the story this late, Leigh can focus on the process of creation rather than its dawn. A single work of art, the writer/director suggests in a narrative so beguiling that its layers of meaning slowly unpeel, is an accumulation of circumstance, attention and care on the part of the artist and his entourage as well, of course, as talent and technique.