Shortly after the suicide bombings on the East Coast in the autumn of 2001, a debate began in the US about whether it could ever be right to use torture to thwart further terrorist attacks.
Most Western liberals were horrified, but we should have been quicker to realise where it might lead: excessive eagerness by some Western security agencies to accept information obtained under torture and a hard-right American administration signing off on rendition, water-boarding and internment at Guantanamo Bay.
It's clear now that one of the unforeseen consequences of 9/11 was a degree of moral confusion at the very top about torture, and a reluctance to be open about it which continues to this day. Even now, quite where the Government stands is far from clear, although a picture is beginning to emerge.
Last week, some sizeable pieces of the jigsaw slotted into place, starting with a robust defence by the head of MI5, Jonathan Evans, of the practice of co-operating with foreign intelligence agencies which use torture.
"Our intelligence resources were not adequate to the situation we faced and the root of the terrorist problem was in parts of the world where the standards and practices of the local security apparatus were very far removed from our own," he said in a speech published on the agency's website.
He denied that MI5 had been involved in torture, although a report from the Intelligence and Security Committee has already revealed that security service chiefs were sufficiently troubled by these issues to appoint an 'ethical counsellor' whom employees could speak to if they had concerns about their work. A dozen members of staff did so.
The UK actually faces two separate sets of accusations, one of which is easier to deal with than the other.
The current line on the Bush administration's interrogation techniques is that the British Government was slow to realise what its closest ally was up to and would have been dismayed had it done so.
According to Tony Blair's intelligence and security adviser, Sir David Omand, the Government "may have been rather slow to cotton on to exactly the nature of the programmes the United States was running".
This implies that ministers wouldn't be so trusting if a similar situation were to arise again, but it has to be acknowledged that achieving this degree of moral clarity with hindsight is quite convenient all round.
I don't think there's much doubt now that the UK adopted a 'don't-ask' policy towards some of the intelligence provided post 9/11 by countries such as Morocco, Pakistan and Saudi Arabia.
Nor do I think that many people would expect a democratic government to ignore a tip-off about a genuine terrorist threat solely because the information came from a regime known to use torture.
If the Saudis were to approach the British Government with information about a bomb plot in London next week, no minister would refuse to act and risk the lives of hundreds of people.
But that's very different from actively soliciting information from foreign intelligence agencies with a record of torture, knowing it could be obtained only under duress.
In last week's second important development, the High Court in London ordered the release of US intelligence documents containing details of the alleged torture in Morocco of Binyam Mohamed, a former Guantanamo Bay detainee.
The judges said unequivocally that it was clear "that the relationship of the UK Government to the US authorities in connection with Binyam Mohamed was far beyond that of a bystander or witness to the alleged wrongdoing".
The Foreign Secretary, David Miliband, has said the Government will appeal but each revelation - and the Government's mulish resistance to it - inflicts further damage and encourages conspiracy theories.
The truth is trickling out and ministers might as well bite the bullet and set up a public inquiry.