Jitney, Royal National Theatre, London

If ever there was a theatrical work that, while true to the drabness of its subject, created something magnificent, it is – no, I'm afraid it's not August Wilson's Jitney. It is the set designer David Gallo's vision of a minicab office in a dying neighbourhood. The only furniture in the bare, bleak room is a discouraged-looking sofa and a desk that no one else wanted – the play could have been staged in a pocket-sized theatre. But, as Wilson uses the lives of the drivers to draw a picture of poor black Americans in the decaying cities of the Seventies, so does Gallo reach up and out to show us walls sagging under the weight of accumulated grime, an abandoned neighbourhood association, and power lines strung across a distant sky.

Not that Jitney is a terrible play. But it is a desultory one, with little of interest to say, and it is unconvincing in its evocation of the period. Barring a reference to Vietnam and another to Muhammad Ali, Jitney might not only be dealing with the Fifties – it could be a play of that decade.

The cosy, all-male world of the office, where the drivers joke and gossip, periodically freezes while one of the men explains what has made him or one of the others the way he is now (service in Korea, a brilliant son doing time for murder).

Youngblood – when I saw this name in the cast list, how I longed for it to be that of an old man, but, no, Youngblood actually is a young blood – Youngblood is working round the clock to surprise his girlfriend with a house for them and their baby. Thinking that he is up to no good, she bursts into the office and starts a row, which turns into a discussion about the importance of trust in a relationship and ends in cute, Fifties fashion with some lovemaking, cut short when another driver comes in and pointedly slams the door.

"Youngblood" would, in fact, have been a better name for Turnbo, a whining, tale-bearing old woman of an old man (the real Youngblood is – why, if the job, in a no-hope area, pays well? – the only driver under 50). Like the other men in Marion McClinton's wonderful cast – if Jitney has few charms for playwrights, attendance should be mandatory for a good many English actors – Stephen McKinley Henderson inhabits his role as casually as if it were an ancient coat, and as majestically as if it were Joseph's.

These men are beaten but proud – even if they have to scourge themselves to maintain their dignity. Telling his criminal son why, in 20 years, he never visited him, Roger Robinson, with an anguish and a hardness that never lapse into self-righteousness, transcends the banality of Wilson's play to achieve the kind of glory that is all too rare this side the grave. The actor stuck with playing the son, however, can do nothing with his peculiar part, and displays a strange lack of affect that suggests he was converted in prison by the Moonies.

In one of the play's many comic moments, the drivers' boss sternly tells them that customers have a right to expect brakes that work. Too often, however, Jitney keeps a foot on the clutch.

In rep until 21 Nov, 020-7452 3000