Big Dada, The Pit Theatre, London

A man sits with a corpse dangled elegantly across his knees. The pose would be a moving pietà – if it weren't for the fact that the living half of this duo is got up in a plastic butcher's apron, African fright wig and blackface, and is busy plucking out and greedily guzzling bloody fistfuls of the dead guys's entrails, an impromptu repast washed down with swigs of whisky. Messengers who rush in with news of a military counter-attack are sent packing. Welcome to the crazed world of Life President Idi Amin Dada, VC, DSO, MC and CBE (Conqueror of the British Empire).

In Big Dada, the all-male black cast of Third World Bunfight, a South African company now visiting BITE, take us on vibrant, cartoon-strip canter through the rise and fall of Uganda's brutal dictator, starting with the coup in 1971 that ousted Obote. Using a well-drilled mix of song, dance and ritual movement, Brett Bailey's production conjures up the macabre madness of a viciously racist regime which booted out all the country's Jews and Ugandan Asians and deflected money needed for health and education to the defence budget, before resorting to mass murder of the opposition and the destruction of everything from the judicial system to the economy.

Sello Sebotsane is a massive and wonderfully magnetic presence in the title role. Jigging about the stage with a model plane in one hand and a Harrods bag in the other as he improvises his megalomaniac foreign policy, he lets you see what was dangerously charming, as well as what was truly appalling, about this figure. A sadistic, monstrously overgrown child like Père Ubu, he also has a winning touch of the boastful Mr Toad. Gradually, though, the personality unravels and, with Sebotsane stripping down to shorts and boxing gloves, we see Amin degenerate into a sweating, psychotic paranoid.

Strong on energy and spectacle, Big Dada is less hot on thematic coherence. The show is dedicated, with pointed irony, to "His Excellency President Robert Mugabe of Zimbabwe", who would not be thrilled by the implied comparison, and there's a likeable Zimbabwean narrator (Michael Sishange) who asks why Africa throws up this kind of dictator again and again. "We as Africans allowed this man to take control," he laments, arguing that the continent must take responsibility for itself and not lay all the blame on the former colonial powers. At the same time, however, there's an undeveloped strand of discontent that – perhaps offering evidence of the continuing colonial legacy – the black cast doesn't have proper ownership of this piece. It's written, directed and designed by a white South African (Brett Bailey): "That's how it is and it makes me sick," declares the narrator. But that contradiction is left unexplored and, though the houselights go up at various points and attention is drawn to the Barbican venue and the predominantly white audience, there's a persistent sense of faintly embarrassed restraint. "I'm raving at the wrong people," says Sishange.

Ending in Amin's jokily self-indulgent rendering of "My Way"(a sequence that feels like the crassest cop-out), Big Dada seems too broad-brush and generalised. You can get more insightful access to this dictator's capricious mentality, and to the corrupting effect of his charisma, in Giles Foden's fine recent novel, The Last King of Scotland, where Amin is viewed through the eyes of the luckless young Scottish doctor who is picked on to be the presidential physician. By comparison, Big Dada merely comes over as showy and shallow.

To 29 Sept (020-7638 8891)