Six years after narrating Gonzo, Alex Gibney's documentary about wild man of the typewriter Hunter S Thompson, Johnny Depp no less enthusiastically hosts this portrait of Thompson's accomplice in the creation of Gonzo journalism - British artist Ralph Steadman. Late in the film, Steadman airs his regret that he hasn't yet convinced the world to see him as an artist rather than a cartoonist - but it's a failing that the film corrects, showing Steadman at work, building up his images from ink splashes, through layers of spraying, scribbling, scratching, erasing. If this process - suggestive of a hybrid between George Grosz and Jackson Pollock - isn't art as much as cartooning, heaven knows what is.
Containing some terrific archive material of the younger, goateed Steadman on the road, Charlie Paul's film gives a historical overview of his adventures and achievements with and without Thompson, eventually offering some sad evidence of the prickliness of the duo's relationship. Even if we don't quite get to know the man, the visionary violence of Steadman's acid pen emerges to vivid effect, partly though Kevin Richards's animations, and despite Depp's sometimes over-eager respect.