Tony Blair warned of US torture claims in 2002
A secret document has emerged in court, revealing Tony Blair's mounting concern in 2002 about claims of torture of terror suspects by US agents.
The former prime minister was briefed by Foreign Office staff as suspects were being moved to Guantanamo Bay.
The document concludes with a hand-written note, said by lawyers to have been written by the former PM.
His note expresses concern about torture claims and urges officials to establish that "it isn't happening".
The memo, sent by the Foreign Office to No 10, emerged amid what is becoming one of the most protracted legal fights in decades.
Six former Guantanamo Bay detainees are suing the British government for alleged complicity in their ill-treatment.
The government denies the allegations - and says many documents relating to what officials knew about US activities cannot be disclosed because they would be damaging to national security. The case is already months behind schedule with complex secrecy arguments yet to be heard by the UK's top judges.
The document said to be annotated by Mr Blair is dated 18 January 2002 and was among a small number of heavily censored papers approved for disclosure.
Marked for Mr Blair's personal attention, the memo explains that an MI5 team had been sent to the US naval base in Cuba to establish how many of the men were British - and what the suspects knew about terror plots against the UK.
The author says that there is "intense" interest in how the men are being treated and that the International Committee of the Red Cross was about to visit the camp.
Underneath, appears the hand-written note which is consistent with other published examples of Mr Blair's style.
It reads: "The key is to find out how they are being treated. Though I was initially sceptical about claims of torture, we must make it clear to the US that any such action will [or would] be totally unacceptable and v. quickly establish that it isn't happening."
The papers include a Ministry of Defence note in which an officer warns superiors about how the US is treating detainees.
That memo, sent five days before the Blair note, says: "It would seem that this detainee issue is one that has the potential to reflect badly on the US/coalition... the US treatment of the prisoners could be judged to be [redacted]".
"It is clear that the US is pushed logistically but my understanding of the Geneva Convention is that this is no excuse."
Lawyers for the six claimants say they want the High Court to set a deadline for the release of material which explains when various parts of government knew the former suspects were being held, mistreated or moved to Guantanamo Bay.
Some 70 government lawyers and officials are sifting through thousands of pages of top secret material relating to what the UK knew about the US's treatment of detainees.
But government lawyers say they cannot comply with demands for faster disclosure of material because documents need to be security vetted.
Earlier in the year, Prime Minister David Cameron proposed the six men enter settlement talks as part of an inquiry on allegations of complicity in torture. But lawyers for the six say they need to learn what the government knew before they can consider negotiations.