That the United States government, under George W Bush and Dick Cheney, sanctioned the use of torture against suspected terrorists in the wake of the 11 September 2001 attacks is no longer in doubt. Even President Barack Obama and his attorney general, Eric Holder, have conceded as much. But what role, if any, did the UK government play?
A series of disturbing revelations over the past month suggests that collusion and complicity in the torture of detainees held overseas may be the darkest legacy of Britain's involvement in the "war on terror".
On 7 July, speaking in the House of Commons, the Conservative MP David Davis claimed that the security services were guilty of "the outsourcing of torture". Speaking under the protection of parliamentary privilege, the former shadow home secretary outlined how MI5 and Greater Manchester Police had colluded in the interrogation and torture of the British terror suspect Rangzieb Ahmed by Pakistani intelligence agents.
On 28 July, a former Guantanamo Bay detainee launched a legal action against the British government for its alleged role in his "extraordinary rendition" to Egypt, where he was tortured. Mohammed Saad Iqbal Madni, a Pakistani citizen held by the United States for six years before being freed, said a CIA flight carrying him to Egypt refuelled on the British Indian Ocean island territory of Diego Garcia.
On 31 July, two high court judges ruled that it was clear that MI5 "must have appreciated" the circumstances of the British resident and former Guantanamo Bay detainee Binyam Mohamed's secret detention at a "covert location", now known to be in Morocco. In their statement, Lord Justice Thomas and Mr Justice Lloyd Jones also revealed that MI5 sent the "US authorities" - or the CIA - questions to ask Mohamed, who says he was tortured.
On 4 August, the joint parliamentary committee on human rights published a scathing report into "allegations of UK complicity in torture", in which it urged ministers to publish the instructions on the detention and interrogation of detainees abroad given to security service officers. "There is now no other way," the report concluded, "to restore public confidence in the intelligence services than by setting up an independent inquiry."
In the US, President Obama has released four secret memos which show that the CIA under President Bush was authorised to torture terror suspects held at Guantanamo and other secret detention sites around the world. There have been no similar disclosures in this country, despite Gordon Brown's promises of a new era of openness and accountability when he took office in 2007. His continued refusal to hold an inquiry into allegations of British complicity in torture is shameful.
So was his earlier insistence that the Iraq inquiry be held in secret. Instructing the Commons intelligence and security committee to investigate the issue, as Mr Brown has done, will not do. In the words of the legal charity Reprieve, this is "a textbook case of the fox guarding the henhouse". The ISC, which failed so miserably to hold MI6 to account over its flawed intelligence on Iraq, and MI5 for its failure to prevent the London terrorist attacks of 7 July 2005, is neither impartial nor independent - it is appointed by, and answerable to, the Prime Minister, and its present chair, Kim Howells, was the Foreign Office minister with responsibility for counterterrorism during much of the time that torture is alleged to have occurred. Why should we trust its conclusions?
The shadow foreign secretary William Hague this past week suggested that even a Conservative government would consider holding an independent inquiry into these allegations. Will Mr Brown allow himself to be outflanked on torture by the Tories?
As the eighth anniversary of the 11 September attacks approaches, it is time for Mr Brown to ensure that the British security services never again turn a blind eye to the abuse of fellow human beings - suspected terrorists or otherwise. Torture is morally unacceptable; it also fails to make us safer and acts as a recruiting sergeant for our enemies. Our opposition to the practice must be non-negotiable. As a senior human rights lawyer remarked in November 2005: "It can never be justified for the government to torture a person or to have a person tortured . . . [That principle] is an absolute." Her name? Cherie Blair. She is one Blair with whom, on this matter, we wholeheartedly agree.