The letters of Martin Mubanga, one of the four British detainees in Guantanamo Bay, published in The Independent on Sunday today, are written in a coded mixture of patois, cockney and rap speak. But they are crystal clear in their depiction of Guantanamo as a moral and legal black hole where, far from the protection of media lenses and international law, human rights are being daily traduced.

The letters of Martin Mubanga, one of the four British detainees in Guantanamo Bay, published in The Independent on Sunday today, are written in a coded mixture of patois, cockney and rap speak. But they are crystal clear in their depiction of Guantanamo as a moral and legal black hole where, far from the protection of media lenses and international law, human rights are being daily traduced.

The stark facts of detentions at Guantanamo still seem like the dystopian setting of a Hollywood film. Our closest ally is detaining British citizens without giving them the basic protections that were afforded to enemy soldiers - including Nazi war criminals - in two world wars. They are labelled "enemy combatants", neither prisoners of war nor ordinary criminals subject to American domestic law. None of the men has been told why he is being held, in violation of basic principles of human rights. The allegations of misconduct can't be verified because the media are barred.

Despite the incalculable damage to the reputation of the US, the Americans remain intransigent in defence of their camp. In response to a Supreme Court ruling granting prisoners the right to know why they are being held, Donald Rumsfeld has established military tribunals that mock all principles of justice. Defendants are not allowed to call witnesses and are denied access to lawyers.

Now even Downing Street is running out of patience. According to court documents, the Prime Minister has "unequivocally demanded" in meetings with President Bush that the prisoners be returned. The Government has given up its attempts to make the military tribunals fair - it is now demanding the men's release. This is a welcome change from the "private criticism, public support" mantra that it has pursued to the point of obsessiveness in its transatlantic relations over the past two-and-a-half years. Ministers spoke of their "negotiations" to secure the men's release, and avoided the denunciations that would have been a reflex reaction if any other state had unlawfully detained Britons. Five months ago, the Foreign Office promised it would ask for a US response to allegations of torture. They are still waiting.

There are two unflattering alternative readings of Mr Blair's attempts to secure their release. Either he refused to make the treatment of detainees a critical issueor his pleas were low on the White House list of priorities. Last week, in the openness of the Lynndie England trial, we saw America exposing its failings at Abu Ghraib before full media scrutiny. It is easy to forget that the US has a tradition of scrutinising malpractice that Britain can learn from. The trenchant criticisms of both the Clinton and Bush administrations in the report of the 9/11 commission made the Hutton and Butler reports seem like anaemic apologies for the establishment.

Sunlight remains the best disinfectant: America badly needs to open up Guantanamo to lawyers and journalists, and afterwards, to give a timetable for when it will be wound down. For as long as it remains open, murky behaviour on a Cuban island will breed contempt for US rhetoric about spreading freedom and the rule of law.