The UK Government must disclose information relating to a Briton held at Guantanamo Bay. He says it supports his case that evidence against him was obtained through torture.
Two judges in the High Court in London said today that they concluded that the Foreign Secretary was under a duty to "disclose in confidence" to Binyam Mohamed's legal advisers in Guantanamo Bay certain information relating specifically to him and "which is not only necessary but essential for his defence".
Mohamed, 30, is facing US military trial and possibly the death penalty if found guilty. His lawyers went to court seeking disclosure of material he says will help defend the charges he faces, which he alleges are based on confessions extracted by torture and ill-treatment.
Lord Justice Thomas and Mr Justice Lloyd Jones were told during a recent hearing that the US authorities denied Mohamed had been subjected to extraordinary rendition or torture.
Mohamed's lawyers said that in a "powerful" judgment the court "has held that the UK Government is under a duty to disclose evidence which it holds about the treatment of Binyam Mohamed between his detention by Pakistani authorities in April 2002 and his subsequent reappearance in Bagram Air Base in July 2004".
A spokesman for the Foreign and Commonwealth Office said in a statement after the announcement: "We are considering the implications of this judgment very carefully.
"We have never contested that Mr Mohamed's defence lawyers should have access to information which would assist him in his defence in any trial at Guantanamo Bay.
"The court recognised the strenuous efforts that we have made to assist Mr Mohamed in Guantanamo Bay, including efforts to ensure that the information HMG holds, which relates to a small part of Mr Mohamed's account of what happened to him, is made available to him for purposes of his defence in any prosecution in the US system.
"For strong reasons of national security, to which the court accepted we were entitled to give the highest weight, we could not agree to disclose this information voluntarily.
"These and other issues relating to national security will be considered at a further hearing next week."
Mr Mohamed's solicitor Richard Stein, of Leigh Day & Co, said: "Today's judgment reflects the abhorrence of decent society at the methods employed by the United States' government in the supposed 'war on terror'.
"It has taken the courts of this country to intervene and reiterate the importance of upholding the rule of law.
"We can only hope that the Foreign Secretary will now reflect on this judgment and provide direct assistance to Binyam's defence team."
Clive Stafford Smith, director of the legal action charity Reprieve, who has represented Mr Mohamed since 2005, described the ruling as a "momentous decision".
He said: "Compelling the British Government to release information that can prove Mr Mohamed's innocence is one obvious step towards making up for the years of torture that he has suffered.
"The next step is for the British Government to demand an end to the charade against him in Guantanamo Bay, and return him home to Britain."
Liberty's legal director James Welch said: "We commend the court's recognition that torture is abhorrent and can never be justified."
During the recent hearing of the case, Dinah Rose QC, for Mr Mohamed, said his evidence was that he was tortured following his detention in Pakistan.
He was then rendered to Morocco where he was subjected to more prolonged and brutal torture after being made to "disappear", she said.
The former Kensington janitor, who is an Ethiopian national, alleges he was repeatedly slashed in the genitals with a razor blade while being held in Morocco.
Finally, he was rendered to Guantanamo Bay in Cuba where he has spent the last four years.
Reading out a summary of the court's conclusions, Lord Justice Thomas said it understood that the evidence against Mohamed consisted of confessions he made at Bagram, in Afghanistan, between May and September 2004 and at Guantanamo Bay prior to November 2004.
He said: "That evidence plainly discloses a case to answer but BM contends that this evidence is inadmissible because it was obtained as a result of a two-year period of incommunicado detention between April 2002 and May 2004 during which he was subjected to torture and cruel, inhuman or degrading treatment at the hands of the Pakistani and Moroccan authorities with the connivance of the United States government and to similar treatment by the United States government itself."
The judge said the Foreign Secretary had declined to disclose any information to Mohamed's lawyers representing him in the Guantanamo proceedings "because he contends he is under no duty to do so and because of his concerns of resulting damage to national security".
Ruling today that there was a duty, Lord Justice Thomas said the court had not yet made a decision on the issues relating to national security.
He said the court "will make no order for the provision of the information" until the Foreign Secretary has had the opportunity to consider the interests of national security in the light of the judgment "and the court has made its decision on those issues at a further hearing and, if the court decides that information is to be provided, has resolved any dispute as to the manner in which it is to be provided".
A significant part of the recent hearing of Mr Mohamed's application took place in closed session due to the national security sensitivity of much of the material before the court.
The judges today handed down two judgments - one closed ruling, available only to special advocates and the Foreign Secretary, and an open judgment.
In the lengthy and detailed open judgment, the court said Mr Mohamed was charged in May with offences which may carry the death penalty and he faced an imminent decision on the reference of those charges for trial before a US Military Commission.
One of the allegations against Mr Mohamed, who converted to Islam, was that he was chosen by al Qaida, because of his refugee status in the UK, to train for and participate in terrorist actions.
Lord Justice Thomas said it was accepted on behalf of the Foreign Secretary that Mr Mohamed had established "an arguable case" of "wrongdoing" relating to his alleged treatment.
It was not necessary for the court to determine whether there "was in fact any wrongdoing by or on behalf of the United States Government".
He added: "It is important to emphasise that we therefore do not do so."
The judge said: "It is clear from the evidence we have seen that every effort has been made by the United Kingdom Government to try and secure BM's return and to provide him with assistance, save for disclosing to his lawyers the documents and information the subject of these proceedings.
"The refusal to disclose is based on concerns of damage to national security that such disclosure might well entail."
The UK Government "has a very strong record in advocating the case against torture and urging other states not to use torture", he said.
Amnesty International UK Guantanamo campaigner Sara MacNeice said: "This is a welcome ruling. Any information that the UK Government holds about how Binyam Mohamed may have been treated must be made available to his legal team.
"If torture or ill-treatment has taken place it should be exposed, investigated and any 'confessions' extracted under torture should be discounted.
"Binyam has already been held in harsh conditions for over six years. According to his lawyer, his mental health has suffered considerably.
"David Miliband should ask the US to move him to a less oppressive part of the Guantanamo prison complex at the earliest opportunity."
She said that ultimately he should be returned to Britain and released or be given a proper trial.
The Guantanamo regime "of harsh conditions, ill-treatment and military show trials should be brought to an end".