The Power of Nightmares assesses whether the threat from a hidden and organised terrorist network is an illusion. In the concluding part of the series, the programme explains how the illusion was created and who benefits from it.
In the wake of the shock and panic created by the devastating attack on the World Trade Center on 11 September, 2001, the neo-conservatives reconstructed the radical Islamists in the image of their last evil enemy, the Soviet Union - a sinister web of terror run from the centre by Osama Bin Laden in his lair in Afghanistan.
There are dangerous and fanatical individuals and groups around the world who have been inspired by extreme Islamist ideas, and who will use the techniques of mass terror - the attacks on America and Madrid make this only too clear.
But the nightmare vision of a uniquely powerful hidden organisation waiting to strike our societies is an illusion.
Wherever one looks for this al-Qaeda organisation, from the mountains of Afghanistan to the "sleeper cells" in America, the British and Americans are chasing a phantom enemy.
But the reason that no-one questions the illusion is because this nightmare enemy gives so many groups new power and influence in a cynical age - and not just politicians.
Those with the darkest imaginations have now become the most powerful.
In part one, the programme looked at the origins of the neo-conservatives and the radical Islamists in the 1950s.
The second part of the series examined how the radical Islamists and neo-conservatives came together to defeat the Soviet Union in Afghanistan.
The Power of Nightmares will be broadcast over three nights from Tuesday 18 to Thursday, 20 January, 2005 at 2320 GMT on BBC Two. The final part has been updated in the wake of the Law Lords ruling in December that detaining foreign terrorist suspects without trial was illegal.