If anyone tried to imagine what a highly skilled, ruthless assassin might look like, Robert O’Neill’s image would not spring to mind. But beyond his friendly face and benign demeanour, O’Neill is a man who has spent much of his adult life learning to kill. In May 2011, every bit of the U.S. Navy Seal’s training was tested when he lined up the western world’s greatest single enemy, Osama bin Laden, in his gunsights. O’Neill didn’t flinch – he pulled the trigger. As Liam Bartlett discovered, hearing his story is chilling enough, but even more worrying are the latest expert warnings that bin Laden’s death, far from killing off al-Qaeda, has spurred the terrorists on to greater evil. Reporter: Liam Bartlett Producers: Phil Goyen, Steve Jackson