The Island, Young Vic Theatre

This near-legendary short play, devised by Athol Fugard with the actors John Kani and Winston Ntshona (who gave their names to its characters), was first shown in Cape Town in 1973, during the apartheid era. Its effect then must have been electric, and some of that visceral intensity still shone out in one of the pair's last performances of the piece at the Old Vic in 2002.

They had performed it many times by then, here and in the United States as well as back home, and their real-life friendship, together with their shared experience of apartheid, had become part of the event, making it a riveting theatrical experience.

But all this reminiscing is hardly fair. At the Young Vic, two experienced but much younger actors, Jimmy Akingbola and Daniel Poyser, are tackling the roles in a fortieth anniversary production and must banish all thought of their famous forebears. Theirs is a different task. Apartheid is no more, Nelson Mandela is free and Robben Island – the site of the prison which gives the play its title – is a tourist destination. And anyway, most of the Young Vic audience are probably too young to remember Kani and Ntshona. Has the play anything to say to Londoners now?

Winston has been condemned to life imprisonment for burning his pass book, the hated identification document all black South Africans were obliged to carry. John's sentence has been overturned on appeal and he will soon be released. They share a cell and know each other intimately, sometimes bickering like an old married couple, sometimes letting anger explode. But they have a strength which no-one can take away: their imagination. It is this which helps them to maintain their humanity, even to transport them, temporarily, out of their circumstances. In an early scene, John (Poyser) uses his tin mug as a stand-in phone and convincingly enjoys "hearing" and responding to replies from people back home in New Brighton, with Winston urgently attempting to join in.

The plot, inspired by real events, is about the preparation of a performance of Antigone. Antigone's defying of the power of the state is obviously pertinent to their situation and Winston goes along, reluctantly at first, with John bossily persuading him into the part of Antigone. In a wig made of teased-out rope, tin mugs for "titties" and a blanket robe, he cuts a comic but ultimately strangely dignified figure.

Alex Brown, winner of the JMK Award for young directors, makes the most of the actors' physical vigour and brings out the terrible contrast between their bantering friendship and their humiliation at the hands of bullying overseers. The effect of the first scene, in which John and Winston work out a punishment by pointlessly shifting piles of sand in silence, is somewhat dissipated, however, by the audience (who face each other either side of a raised stage in the Clare studio) entering and chatting. That long, relentless silence could be unbearable. And the final scene, in which Winston expresses his fury through the filter of Antigone would be even stronger with fewer knowing nods and winks from John.

But this is generally a taut, confident revival of a play which still has plenty to say, not only about friendship but about the possibility of holding on to dignity in the worst of circumstances. It is also, of course, about the liberating power of theatre.

• The Island at the Young Vic until November 30