High Court judges have been told there is "compelling vidence" Guantanamo Bay detainee Omar Deghayes and two other British residents had been severely tortured and suffered inhuman and degrading treatment.
Timothy Otty, appearing for the three detainees, said the men also remained exposed to a "real risk" of further ill treatment at the detention facility in Cuba.
He described the "distress" the families of the men were having to endure.
The Argus has been campaigning for justice for Mr Deghayes, from Saltdean, calling for him to either be brought to trial or released. Yesterday, Mr Otty was asking Lord Justice Latham and Mr Justice Tugendhat, sitting in London, to declare "legally unsustainable" a refusal by Foreign Secretary Jack Straw to petition for the release of Mr Deghayes and two fellow detainees.
The Government has maintained that, as foreign nationals, Bisher al-Rawi, Jamil el-Banna and Mr Deghayes have no legal right to the assistance they seek.
But Mr Otty said that it had become clear yesterday morning that, at least in the case of Mr al-Rawi, "it has now been conceded that the Foreign Secretary will be making representations" because of the particular circumstances of his case.
Christopher Greenwood QC, appearing for the Foreign Secretary, told the judges that the Government was "attaching considerable weight" to a denial by the US that torture or inhuman treatment had taken place at Guantanamo Bay.
The British Government itself did not have independent evidence of what was happening and would "certainly not accept that there was compelling evidence that the men have been tortured".
Mr Otty asserted there was compelling evidence before the court. He added: "The suffering with which this case is concerned is not limited to the detainee claimants. Family members, who are British citizens as well as residents in the country are experiencing the most intense distress."
Mr Deghayes and the two other detainees in yesterday's case are all long-term residents of the UK, although not British citizens.
Mr Deghayes was detained in Pakistan. His name was said to be on the FBI's "most wanted" list. But his legal team says the photograph in his file was of a "totally different individual".
His lawyers maintain that Mr Deghayes has been rendered virtually blind in one eye during his detention, yet was still being constantly subjected to high light levels.
More than two years ago Lord Steyn, a member of the House of Lords judicial committee, condemned the "utter lawlessness at Guantanamo Bay", where people were being detained indefinitely without trial.
The nature of the detentions had been condemned by United Nations rapporteurs, who had concluded that techniques authorised for use there might amount to torture.
The hearing continues today.
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