When Nicholas Kent's latest trial-by-theatre tribunal staging opened at the Tricycle last month, the vaguest hint of smugness hung over proceedings. You couldn't fault its raison d'etre. If ever there was a case for another dose of Kent's widely admired verbatim stagings, Guantanamo and the Coalition's infamous treatment of detainees was it.

Terrible infringements of individual human rights have been applied by the US and the UK in the name of freedom. And almost to the day of the Tricycle opening, those pictures of Abu Ghraib prison started seeping into our public consciousness. Some reckoning had to be made and Kent and the Tricycle with sublime timing were there.

Yet, though directed by Kent (with Sacha Ware) with his usual restraint and refusal to indulge in histrionics - just telling how it is using the actual words of the detainees themselves and their relatives, culled and edited by Victoria Brittain and Gillian Slovo, two writers and journalists of impeccable credentials - the tacit acceptance of shared assumptions gave it an uncomfortable feeling of self-righteousness.

In the New Ambassadors, I'm happy to say, some of that element has gone. Now it emerges simply as a desperately moving wake-up call.

Guantanamo deals with the stories of British detainees. (Since then, of course, stories of abuses at other US camps, in Afghanistan, have come to light). Framed within Miriam Buether's wire-mesh cages and haunted by Islamic prayer calls, we hear accounts from the father of one of them, Moazzam Begg, still incarcerated in Guantanamo; we hear and see Moazzam, resilient at first, starting to crack after a year in solitary confinement. We hear from the remarkable Jamal al-Harith, one of the five freed Britons, who with truly remarkable laconic Mancunian wit recounts the absurdity and terror of his capture and interrogation.

Many other characters come into this scenario - British and American civil and military lawyers, British MP's; even Donald Rumsfeld and Jack Straw make brief if caricatured appearances.

What results, apart from a mounting sense of shame at British collusion and the individual injustices, is the awareness of how, under conditions of national paranoia, it is the innocent who suffer.

Guantanamo is too one-sided to really tell us how we've got to the place we are. The brother of a young British woman `murdered' on 9/11 puts some of the subsequent events into a kind of context. But it isn't really sufficient.

Go and see Guantanamo, though, for what it reveals about farce as a component of horror, for the boot up the backside it gives us all about allowing these things - detention without trial, dehumanisation, torture - in our name. And most of all for what it shows us about the fragility and corruption of language. At Guantanamo, `suicide' is turned on its head and becomes `manipulative injurious self-behaviour.'

- Carole Woddis