In this two-part series, Secret Pakistan, a number of middle-ranking Taliban commanders give detailed accounts of how Pakistan, and in particular its security service, the ISI, have helped train, arm and supply Taliban forces that have been killing British soldiers.
In the 1990s Pakistan helped create the Taliban to prevent Afghanistan falling under the influence of India, their enduring enemy.
According to one active Taliban commander, who fights under the name Mullah Qaseem: "For a fighter there are two important things – supplies and a place to hide. Pakistan plays a significant role. First they support us by providing a place to hide which is really important. Secondly they provide us with weapons."
Other Taliban fighters describe how they and their fighters were, and are, trained in a network of camps on Pakistani soil.
According to a commander fighting under the name of Mullah Azizullah the experts running the training are either members of the ISI or have close links to them: "They are all the ISI's men. They are the ones who run the training. First they train us about bombs; then they give us practical guidance. They are present during the training."
Another Taliban fighter, known as Commander Najib, says Al Qaeda trainers also operated in the camps, talent-spotting possible suicide bombers: "I was in the camp for a month... They were giving us practical training in whatever weapons we specialised in ...suicide bombers were taken to a different section and were kept apart from us. Those who were taught to be suicide bombers were there..."
According to Richard Kemp, Head of Intelligence, Cabinet Office 2001-2006: "It was quite clear to us that the Pakistanis were playing very much a double game and a lot of what they were saying and some of what they were doing was, was very clearly aimed at the, the eyes of the West and didn't necessarily reflect their real intentions and their real actions.
"Over a number of years I'd been monitoring international terrorist activity not just in the UK but around the globe and I'd seen in virtually every case links back to Pakistan so it didn't come in any way as a surprise to find that terrorists operating in the UK were being directed by Al Qaeda leaders in Pakistan...
"The ISI of course... must take responsibility for the fact that some of these camps were still up and running including perhaps the camp that, that was responsible for training the 7/7 attackers."
Yet initially the evidence of Pakistan's double role was largely disregarded.
According to the former British Ambassador to Afghanistan Sherard Cowper Coles: "Somehow because the Pakistani dimension was too difficult, too enormous, we just sort of shut it out and pretended that by pushing the insurgents around Helmand or out of bits of Helmand, that was somehow solving the problem."
The series reveals that by 2009 evidence of a double cross was too strong to be further ignored.
Bruce Riedel, a former CIA officer, who headed a secret review of Pakistan's role for President Obama, describes briefing the President: "I spoke pretty much non-stop for about 45 minutes, and then we spent another hour, hour and a half, talking about it...
"I told the President Pakistan was double-dealing us and that the Pakistanis had been double-dealing the United States and its allies for years and years, and they were probably going to continue to do so."
Since then relations between Pakistan and the US have in secret verged on hostility – explaining why Pakistan was not informed of the US raid that killed Bin Laden – even though publicly Pakistan is meant to be a key ally.
The series hears testimony that Afghan intelligence shared information with Pakistan's President Musharraf about Osama Bin Laden's whereabouts in 2006, suggesting he was hiding in a town just 12 miles from Abbottabad – where Bin Laden finally was discovered and killed earlier this year.
The Head of Afghan Intelligence at the time alleges the information was not acted on.
Amrullah Saleh, Head of Afghan Intelligence from 2004-2010, discusses information gained via a Pakistani believed to be smuggling guns to the Taliban, Syed Akbar: "The most revealing and shocking part of Syed Akbar's story is he... confessed to us that he escorted Bin Laden from one location to another. And the information we had was suggesting Manshera was the town where Bin Laden was hiding... It happens after so many years that Bin Laden was about 12 miles from that location."
Saleh and the Afghan President Hamid Karzai took the evidence to President Musharraf of Pakistan who they claim reacted angrily. According to Saleh: "He [Musharraf] banged the table and looked at President Karzai and said, am I President of banana republic? If not, then how can you tell me Bin Laden is hiding in a settled area of Pakistan.
"I said well this is the information so you can go and check it. It happens after so many years that Bin Laden was about 12 miles from that location. Why they should be so blind of the fact of the environment within their own country?"
Pakistan strongly denies the allegations. General Athar Abbas, Director General of the Inter Services Public Relations and official spokesman for the Pakistan Military, said: "To say that these militant groups were being supported by the state with the organised camps in these areas... I think nothing could be further from the truth."
Adds General Ashraf Qazi, Director General, Pakistan Intelligence, ISI (1993-5): "If you look at the wanted list which the US issued, most of those guys had actually been nabbed by ISI... Unfortunately, one guy we missed, that's the number one guy. And so we got all the blame." (credits- BBC Two)
