The CIA used a secret base at Guantanamo Bay, nicknamed Penny Lane, to turn some of al-Qaeda's most dangerous terrorists into double agents, US officials have admitted.
Inmates languishing under the camp's harsh regime were offered cash rewards, hotel-style rooms and even pornography if they agreed to help the CIA track down and kill fellow al-Qaeda operatives.
Instead of Guantanamo's spartan cells, they would be transferred to cottages equipped with private kitchens, showers and televisions, as well as their own patio.
A handful then signed agreements to work for the CIA, under which they were released and told to hook up once more with their former comrades. The programme, set up when President George W. Bush was in the White House, was potentially a huge gamble for the CIA, because of the risks the "turned" inmates would simply rejoin al-Qaeda's ranks.
There were also fears that they might pass on false information to provoke inaccurate drone strikes on civilians in al-Qaeda strongholds in Afghanistan and Yemen.
Another concern was that an inmate who had been through the programme would take part in a terrorist "spectacular" and then publicise the fact that he had been on the CIA payroll.
Details of the Penny Lane facility, which operated between 2003 and 2006, were disclosed by AP, which based its report on anonymous interviews with nearly a dozen current and former US officials.
Also nicknamed The Marriott because of its comfortable conditions, Penny Lane's biggest luxury in inmates' eyes was its beds, which were proper mattresses rather than military issue-style cots. Its name was a nod to the Beatles song. Another secret facility at Guantanamo Bay was known as Strawberry Fields and was used to hold "high-value inmates". It got its nickname from the song Strawberry Fields Forever, through the threat that the detainees would be held there forever.
Officials said of 779 people who were taken to Guantanamo Bay, only a few dozen were ever considered for Penny Lane, and only a fraction actually went on to work for the CIA.
All were paid from a secret CIA account code-named Pledge, but although millions of dollars were paid out, it is unclear whether any of the double agents ever provided useful information that led to an al-Qaeda agent being killed or captured. Some stopped providing information and the CIA lost touch with them.
Officials also said that al-Qaeda suspected all along that they would attempt such a programme. As a result, the movement became suspicious of letting former Guantanamo Bay detainees back into their inner circle.