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.

So is the world's most wanted man still alive?

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".

"We don't have a clue where he is," he says.

In the absence of any concrete intelligence, Bin Laden has become shrouded in myth and rumour.