Osama Bin Laden died eight years ago during the battle for Tora Bora in Afghanistan, either from a US bomb or from a serious kidney disease.

Or so the conspiracy theory goes.

The theory that has developed on the web since 9/11 is that US intelligence services are manufacturing the Bin Laden statements to create an evil bogeyman, to justify the so-called war on terror in Afghanistan, Iraq and back at home.

Bruce Riedel, who chaired President Barack Obama's Afghanistan/Pakistan policy review, and who has seen the intelligence on Bin Laden, says the trail has not so much gone cold as "frozen over".

Numerous audio and video statements purporting to be from Bin Laden have been released, but their authenticity has been continually questioned.