Since 11 September 2001, the CIA has been systematically seizing suspects and sending them, without legal process, not only to Guantanamo Bay but to regimes such as in Egypt, Jordan, and Syria. Human rights campaigners say the system, officially known as "extraordinary rendition" is a system of torture by proxy.
Britain maintains the main reason it will not deport prisoners being held without charge at Belmarsh prison is the fear they will be tortured or otherwise abused by their home country. But a series of cases has emerged which, critics say, exposes the Government's dishonesty by suggesting information provided by Britain about its citizens and residents has led to the capture and eventual torture of Islamic terrorist suspects.
Britain is also an operational base for two executive jets regularly used by the CIA to carry out so-called "renditions". One Gulfstream jet - used for taking prisoners to Egypt and Jordan from countries including Sweden and Indonesia - has called regularly at Luton, Glasgow, Prestwick, and Northolt airports.
A Boeing 737 jet, used for the transfer of prisoners, passed through Glasgow Airport on Monday morning on its way to Iraq. Both jets are white and unmarked, apart from their US civilian registration. Inquiries suggest they are owned by US companies that exist only on paper and which are almost certainly a front for the CIA.
Michael Ratner, the director of the Centre for Constitutional Rights, which is representing several former prisoners who were "renditioned", said: "It is a secret process. No one really knows what happens in the rendition process or in the gulag of secret CIA hell holes [where some prisoners are sent]."
One notorious rendition occurred in Sweden in December 2001 when a team of masked US agents arrived to transfer two Egyptian dissidents, both accused of terrorist involvement, to Cairo. Both complained later of brutal torture.
But there is evidence that intelligence originating in Britain may have been behind the CIA's involvement in the seizing of least one of the Egyptians, an asylum-seeker named Mohamed al-Zery, who, after months of torture, was eventually cleared and freed.
Yassir al-Sirri, an Islamic activist living in London who is accused by Egypt and America of having al-Qa'ida connections, said that, in the weeks before his own arrest in London in October 2001, he had been in touch with Mr Zery, who wanted help with collecting information with his asylum claim.
Speaking to BBC Radio's File on Four, Mr Sirri said that when British anti-terrorist officers raided his home, they took his computer and his fax records and those were passed to the Americans.
"Later in Sweden this man, Mr Zehry, was arrested and this information could only have come from the British authorities. They are completely responsible. It's criminal," Mr Sirri said.
Mr Sirri later discovered that, in the following weeks, contacts of his around the world were seized, one by one. Mr Sirri, who runs an Islamic media centre devoted to exposing any human rights abuses, had contacts with many families of prisoners.
Mr Sirri had been arrested over accusations he was involved in the murder of the Afghan leader, Ahmed Shah Masood, but he was cleared when a UK judge described him as an "innocent fall guy". Efforts by both the US and Egypt to extradite him for alleged links to terrorism have failed.
In Stockholm, Kjell Jonsson, Mr Zehry's lawyer, said he also believed that information passed by Britain was the only explanation for his client's arrest and the involvement of American agents.
The practice of sending suspects abroad for coercive interrogation gathered pace in the aftermath of 11 September, 2001, when a senior counter-terrorism officer, Cofer Black, openly admitted that after the al-Qa'ida attacks "the gloves came off'.
The procedure was supported by legal memos drafted by the new Attorney General, Alberto Gonzales, which claimed the Bush administration was not restricted by the Geneva Conventions when dealing with suspects from the so-called war on terror.
Michael Scheuer, a former senior CIA official involved in setting up the system, said: "The practice of capturing people and taking them to second or third countries arose because the Executive assigned the job of dismantling terrorist cells to the CIA.
"When the Agency came back and said `where do you want to take them?' The message was - `that's your job'."
Mr Scheuer claims there was legal oversight in every renditioning case and yet he admitted suspects were tortured.
"The bottom line is, getting anyone off the street who you are confident has been involved or is planning to be involved in operations that could kill Americans is a worthwhile activity."
Just how many suspects have been subjected to renditioning is unclear.
Critics point out that the US does not permit suspects access to lawyers. They liken the secrecy to that which is surrounding the network of secret detention centres operated by the CIA around the world in places such as Afghanistan, Iraq, Guantanamo Bay, on US ships and on any number of locations that have not been publicly disclosed.
But the planes used by the CIA have left a trail. The Gulfstream, then registered as N379P, was first spotted landing at Shannon Airport, Ireland, in spring 2003. Its registration number, since changed, was logged by members of a peace camp. They only learned it was the rendition plane when they were later contacted by Swedish journalists investigating the torture of the two Egyptians.
"It just looked like a civilian plane," said Edward Horgan, 59, from Limerick, one of the witnesses to its landing.
American journalists have revealed the plane is formally owned by Bayard Foreign Marketing, which lists its headquarters as the address of a lawyer in Portland, Oregon.
There is no evidence that Thomas Bayard, whose signature appears on documents filed with the local authorities, is a real person. When The Independent called the firm, there was nobody there, just an answering machine.
The allegations that Britain is co-operating with the "rendition" system are also bolstered by arrests in The Gambia, West Africa, where four British residents were arrested and questioned by US agents in November 2002, apparently after a tip-off from British authorities.
Wahab al Rawi, an engineer whose family fled persecution in Iraq, was surprised to be questioned in the Gambia by US agents when he had already been interviewed and freed by Britain's security service, MI5, back in London.
They had been asking him about his family's friendship with Abu Qatada, a radical Islamic cleric now in detention at Belmarsh prison. When Mr Rawi asked to see the British High Commissioner, he said he was told "who do you think ordered your arrest?"
Though Mr Rawi was released, his brother Bisher and a business partner, Jamil al-Banaa, were picked up by the Americans, apparently in the Gulfstream. They are still being held in Guantanamo Bay.
Another case pointing to Britain's involvement is the arrest of Martin Mubanga in Zambia. Last weekend, after being freed from Guantanamo Bay, he alleged his original arrest came after the involvement, and accusations made against him, of a British MI6 officer.
Craig Murray, the former British ambassador to Uzbekistan, has also accused Britain of complicity in torture, because of the use that MI6 makes of the intelligence gathered in this way by CIA.
He said many prisoners of Uzbek origin captured by American forces were taken back to Uzbek jails where they received the most brutal tortures.
These interrogations ended up in MI6 reports that he received. "I was told by the Foreign Office's senior legal advisor there was nothing in law to prevent us obtaining and using material which had been extracted under torture provided that we had not ourselves done the torture.
"And MI6 said they found the intelligence useful. I was shattered and disillusioned."
A Foreign Office spokesman said Britain condemned torture but could not ignore intelligence from sources. "Without the sharing of intelligence, there would have been many more bloody terrorist attacks that would have gone ahead, like the plan to bomb a Christmas market in Strasbourg.
"If you have an agreement to work together against terrorism with another country then it's obvious common sense that one has to have a certain amount of trust in that country and in the way it chooses to use that intelligence."Reuse content