Bridget Kendall discusses the roots and reach of Islamist terrorism from Afghanistan to Africa. The historian William Dalrymple looks back to Britain's First Afghan War where many Afghanis rose in answer to the call for jihad. Nadeem Aslam's latest novel ranges across the Afghan-Pakistan border where the past and the present are locked together. Dr Christina Hellmich explores what has happened to al-Qaeda since Osama bin Laden's death. And as David Cameron calls the response to Islamist terrorism in North Africa a "generational struggle", the political analyst Imad Mesdoua looks at the parallels with Afghanistan.
Producer: Katy Hickman.