The Secret War on Terror reveals the astonishing inside story of the intelligence war which has been fought against Al Qaeda over the last decade since 9/11.

This episode looks at how, with harsh interrogation techniques increasingly off-limits, spy agencies, have developed a controversial high-tech method of targeting and killing suspected terrorists with pilotless drone aircraft.

Laura Poitras' film tells how two men whose lives were caught up with Al Qaeda leader Osama bin Laden ended up taking very different paths after the invasion of Iraq.