Right show, wrong critic. In asking comedy reviewers to see Basic Training, presumably because it tells the autobiographical story of an aspiring comedian who joins the United States Air Force, the publicists have missed a trick. Kahlil Ashanti is a terrific, versatile actor and stand-up is the least of his talents.

In this rollercoaster monologue, Ashanti plays 21 characters, ranging from abusive stepfather to predictably flamboyant concert party colleagues. Highlights include a foulmouthed central casting Sarge ("I'll reach into yo' ass and pull out yo' tonsils") and a militant uncle, who sees pool as metaphorical racism, with whites determined to clear the table of other colours.

But calling this a comedy is a foul shot. The real meat is the eloquent star's emotional quest to discover his real father. This is the core of the piece, prompting numerous heartstopping moments.

One can see why Hollywood is turning Basic Training into a movie. There are too many gear changes, as Ashanti spins from goggle-eyed slapstick to melodrama, but a solid narrative underpins the clowning.

This is a formidable tale about racism, relationships and reconciliation. Anyone expecting a Gulf War It Ain't 'Alf Hot, Mum will feel short-changed.

• Until 4 November. Information: 020 8237 1111, www.riversidestudios.co.uk.