Panorama: The Missing Stolen School Children

The world was outraged when it emerged that Boko Haram militants had kidnapped 276 girls from a school in Chibok town in Nigeria. Over a year later, most of those girls are still missing. Tulip Mazumdar tracks down women and girls who have escaped from Boko Haram. Those held alongside the Chibok schoolgirls reveal how some have been forced to 'turn', becoming deeply radicalised and joining the militant group