David Miliband won something of a hollow victory over the media last week. The foreign secretary persuaded two judges not to publish ‘seven very short paragraphs’ they had withheld from a judgment last August.

These 25 lines summarised reports to British security and intelligence officials by the US government about its detention and treatment of Binyam Mohamed from 2002 to 2004. The summary is ‘highly material’ to allegations that the former British resident was tortured.

US interviews with Mohamed were ‘facilitated’ by Britain’s security service. If the MI5 officer who interviewed Mohamed had assisted others to torture him, he could face war crimes charges in Britain.

Miliband’s evidence persuaded Lord Justice Thomas and Mr Justice Lloyd Jones that, if they restored the paragraphs omitted from their earlier judgment, there was a real risk that the US government would reduce the intelligence it gives Britain. That could ‘inflict on the citizens of the UK a very considerable increase in the dangers they face’.

A day later, though, Miliband told Parliament that ‘the US authorities did not threaten to "break off" intelligence co-operation with the UK’. Mohamed’s solicitor, Richard Stein, said there was a ‘substantial difference’ between that and what the foreign secretary had told the two judges. For that reason, Stein has asked the High Court to re-open the case.

What was not noticed by reporters last week was the interest of Britain’s most distinguished former judge.

Stein and his firm Leigh Day & Co were instructed by an organisation called Reprieve, which holds a power of attorney for Mohamed. Reprieve was founded in 1999 by Clive Stafford Smith to provide legal support for prisoners around the world – initially, US inmates on death row and now detainees at Guantanamo Bay. Since the beginning of this year, the chairman of Reprieve has been Lord Bingham.

The former senior law lord spoke to me about his interest in Mohamed’s case last week, a day before judgment was delivered.

Leaving aside the case of Baha Mousa, the Iraqi hotel worker beaten to death by British troops in 2003, Lord Bingham says it is his impression that the British authorities have not connived at the mistreatment of prisoners abroad.

‘But it may be that the papers that come to light in Binyam Mohamed’s case will give the lie to that; I don’t know,’ he says. If British officials had connived at mistreatment of prisoners abroad, that would cause Lord Bingham great concern.

The former judge was looking fit and relaxed when I called on him at his London home. Since reaching the mandatory retirement age of 75 last autumn, he has been teaching students as a visiting professor at Oxford and doing some international arbitration. Though too old to become first president of the new Supreme Court this year, he remains president of the Hay literary festival and has just completed a book on the rule of law.

This will enlarge on a magisterial lecture he gave in Cambridge in 2006, in which he summarised the rule of law as requiring that ‘all persons and authorities within the state, whether public or private, should be bound by and entitled to the benefit of laws publicly and prospectively promulgated and publicly administered in the courts’.

So as not to disqualify himself from ruling on the subject if it came before him judicially, Lord Bingham had avoided saying whether he thought Britain’s invasion of Iraq in 2003 had been lawful.

That had to wait until his Grotius lecture last November, by when he was free to say that Lord Goldsmith’s advice supporting military action had been ‘flawed in two fundamental respects’. More broadly, he argued that the rule of law applies just as much in the international sphere as it does in the national one.

‘It’s not a very striking principle to assert, but when times are rough there’s a temptation to forget about it,’ he says.

Is he thinking of Guantanamo Bay? ‘Guantanamo would be a very good example. So would extraordinary rendition or resort to enhanced interrogation techniques.’

Now that President Obama is set to close Guantanamo, Reprieve’s role will change. Instead of trying to have detainees released, it will now work to get them placed in countries that will accept them.

Should Britain take any more? Lord Bingham mentions Mohammed el Gharani, a Chad national living in Saudi Arabia who travelled to Pakistan and was sold to the US for bounty at the age of 14.

It was alleged that he was part of an al-Qaida cell in London, even though British officials should have known he had never been to England and would have been 11 at the time.

Last month, Reprieve obtained a federal court ruling that el Gharani was not and had never been an enemy combatant. After seven years in Guantanamo, he is about to be released.

The thought that a 21-year-old could have been wrongly detained for a third of his life causes Lord Bingham ‘almost indescribable dismay’. He thinks that ‘quite a strong case’ could be made for allowing el Gharani to settle in Britain if he wants to.

Lord Bingham understands that the US government saw the need to act decisively in response to the attacks of 11 September 2001. ‘But I don’t really have any sympathy, because the whole point of sending people to Guantanamo was to deprive them of their rights.’

For a judge who is still devoting his energies to upholding the rule of law, nothing could be more offensive.