The title is incongruous, it makes it sounds like a rock opera or concept album. But that does put us in the right era, the late 60s, a time when socialism was a blueprint for revolutionary change not a way to smear Joe Biden, and the police were pigs, not occasional bad apples.

In the ghettos of Chicago, the ability of young Black Panther activist Chairman Fred Hampton (Kaluuya) to unify protest groups from different communities has captured the attention of FBI boss J Edgar Hoover (Martin Sheen under a coating of putty.) Bill O'Neill (Stansfield) is a small-time crook who gets caught trying to steal cars using a fake FBI badge. Threatened with considerable jail time, the man from the bureau Plemons persuades him to go undercover and infiltrate the Panthers.

The most striking thing about this dramatization of the FBI and the Chicago police force's relentless and brutal campaign of harassment against the Panthers and its leader, is the decision to concentrate on the Black Messiah more than the Judas.

In dramatic terms, the morally conflicted, living on his nerves informer is the obvious focal point, while Chairman Fred - inspiring orator, brave and humble leader, flawless hero - should be dramatic dead weight. King's film though largely shuns the mechanics of the traditional informant crime drama. There is only one scene where his cover is almost blown.

Like the FBI, the film is only interested in O'Neill as a way of getting to Fred. Good choice. Two-faced rats are dime a dozen these days, genuine moral leadership though is worth a damn. Kaluuya is exceptional as Chairman Fred. In theory, playing a charismatic orator shouldn't be too great a challenge for an actor (surely, being good at talking is what you learn at RADA) but the contained force of Kaluuya's performance gives humanity to a figure who is written as saintly. Watching him you assume he's a little young for the role, that this fresh face couldn't possibly command groups of people.

At the end it's revealed that Hampton was just 21 years old at the time and that Kaluuya is actually a decade too old for the part.

4/5 stars

Directed by Shaka King. Starring Daniel Kaluuya, LaKeith Stanfield, Jesse Plemons, Dominique Fishback, Ashton Sanders and Martin Sheen. Running time: 126 mins.

http://www.halfmanhalfcritic.com/ for reviews of Primer, out on Arrow Video, and the Criterion Collection release of The Grand Budapest Hotel.