At a time when British theatre seems scared witless of politics, it is exhilarating to see this play back on a major stage. Created by Athol Fugard, John Kani and Winston Ntshona and first seen 25 years ago at the Royal Court, it has, if anything, gained with time. Apartheid may have crumbled, but the play's celebration of defiance and awareness of the human cost of incarceration remain timeless.

Its setting is Robben Island and its subject is imprisonment: the way it both unites and divides, affirming the resisting spirit while punishing the vulnerable body.

John and Winston, the names of the characters as well as the actors, have shared a cell for three years and their relationship has become like an asexual Beckettian marriage. At first we see them mimetically shifting sand in a meaningless Sisyphean labour. Back in their cell, having tended each other's wounds, they prepare a scene from Antigone: John is bullyingly dominant, Winston fearful of public humiliation. But the crunch comes when John learns that a commutation of his sentence means he will be released in three months while Winston will do life.

This arbitrary divorce releases covert tensions and yet makes possible the performance of Antigone's trial and punishment.

Politics and art miraculously coalesce. Quite obviously, the play is a protest against a brutal system. But the play also makes a complex statement about imprisonment.

The two men enjoy the testy togetherness of married partners. But John's provisional release is also divisive. When Winston cries: "Your freedom stinks and it's driving me mad" it both expresses Winston's envious rage and questions the meaning of freedom in the South Africa of the 1970s. As in all good political theatre, and as in Antigone itself, there is both irony and ambivalence.

The piece is now inseparable from its two superb performers; and what is astonishing watching Athol Fugard's production, now supervised by Peter Brook, is how the passing years have enriched their molten relationship. It's not just that the opening scene requires even more Herculean effort. They are so finely tuned to each other's responses that they do seem to be cellmates.

This revival could have been an act of cultural piety, but has become a piece of living theatre: it transcends the moment of its creation to express permanent truths about strategies of survival wherever oppression and unjust imprisonment prevail. It also reminds us that the best political theatre is always vibrant, compelling art.

Until February 26. Box office: 0171-452 3000

This review appeared in some editions of yesterday's paper