How did the world's most wanted man evade capture?

Osama Bin Laden is held responsible not just for the nearly 3000 who died in the terror attacks of 9/11 in America but for thousands of other killings around the world for more than 20 years.

American officials have long believed Bin Laden was hiding somewhere in a mountainous region along the Pakistan-Afghanistan border.

However, there had been no reports of his whereabouts for some years and the trail appeared to have gone cold.

John Simpson reports.