A British resident facing the death penalty at Guantanamo Bay as a terror suspect won a High Court case yesterday over secret Foreign and Commonwealth Office documents that might help to prove that he was tortured.

Binyam Mohamed, 30, insists that he admitted to plotting a dirty radioactive bomb attack on the United States only after torturers had sliced his penis with a blade.

Judges asked David Miliband, the Foreign Secretary, to think again about his refusal to let the Muslim convert’s lawyers see papers that might help to clear him at a military tribunal. The case shed fresh light on how the British security services had cooperated with the US in the interrogation of terrorism suspects who were moved from country to country and held in secret locations.

“The relationship of the United Kingdom Government to the United States authorities in connection with BM [the detainee] was far beyond that of a bystander or witness to the alleged wrongdoing,” the court said.

A British spy had interviewed Mr Mohamed. When America later refused to tell MI5 where he was being held, the security agency sent questions and information to the US to help his interrogators. Mr Mohamed, who was born in Ethiopia, came to Britain as a teenage schoolboy and, although he was refused asylum, he was granted permission to remain in the country in 2000. He studied engineering in London but in June 2001 he went to Afghanistan. He said that he had wanted to kick a drug habit and see for himself whether the Taleban were running a good Islamic country.

In April 2002, after the War on Terror began, Mr Mohamed was arrested at Karachi in Pakistan for trying to fly to London on a false British passport. American authorities informed their British counterparts that Mr Mohamed was plotting to build and detonate a dirty bomb. MI5 sent an officer to interview the suspect.

Mr Mohamed was being detained illegally in Pakistan without access to a lawyer, the High Court decided.

The MI5 officer telegrammed his superiors, saying that the detainee had admitted obtaining his British passport from a criminal. Mr Mohamed also admitted that, after attending mosques in London, he had been recruited to travel to Afghanistan to learn about weapons and explosives. When the Taleban were ousted, he learnt how to use devices against the US forces.

Mr Mohamed said that he had been asked to return to Britain to produce passports. He told MI5 that the dirty bomb story was “an FBI perception”.

The MI5 officer reported: “It was, however, clear that, while he appeared happy to answer any questions, he was holding back a great deal of information on who and what he knew in the UK and in Afghanistan.”

The spy concluded that Mr Mohamed was lying. “[BM] is intelligent and patient. If he chooses not to cooperate he had the personal qualities and strength of will to maintain his story indefinitely. He showed no signs of being anxious about his position. I suspect that he will only begin to provide information of genuine value if he comes to believe that it is genuinely in his interests to do so. I don’t think he has yet reached this point.”

The spy told the suspect that, only if he cooperated fully and told the complete truth could MI5 help by exploring with the Americans “what could be done for him”. Mr Mohamed claims he told US agents that he would refuse to speak to them until he had seen a lawyer. The agents said, however, that the law had changed and there were no lawyers.

He was hung by leather straps around his wrists so that he could only just stand, and fed every second day. He said that the Americans told him: “We can’t do what we want here; the Pakistanis can’t do exactly what we want them to do. The Arabs will deal with you.”

The detainee claims that the Americans then took him to Morocco, where he was severely beaten, deprived of sleep and had his genitals cut with a scalpel.

After being flown back to Kabul, he claims to have been held in a black hole in a prison, beaten and hung up. He was flown to Bagram, then Guantanamo Bay. In both places, under torture, he said that he had confessed “to anything those inflicting that treatment on him wanted him to say”.

He has been charged with conspiracy, with Osama bin Laden and others, to murder and attack civilians. US authorities claim that Khalid Sheikh Mohammed, the alleged September 11 mastermind, instructed the British resident to rent flats in America, fill them with gas and blow them up.

“It might have been thought self-evident that the provision of information as to the whereabouts of a person in custody would cause no particular difficulty, given that it is a basic and long-established value in any democracy that the location of those in custody is made known to the detainee’s family and those representing him,” the High Court stated.

Clive Stafford-Smith, of Reprieve, said: “The British Government may have been accused of being Bush’s poodle but the British courts remain bulldogs when it comes to human rights.” The Foreign Office, which has urged the US to free Mr Mohamed, said that it was studying the judgment.

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