Men freed from the same prison in 2011 went on to play senior roles in Isil, al-Nusra and other extremist groups. Why they were released – and who later killed them – are some of the key questions of Syria’s brutal war.
One was struck down by a missile in Damascus. Another, Jihadi John’s boss, was taken out by an American “pinpoint strike”.
The third died with a bunch of comrades in Turkey in a mass killing of Syrian rebels that has still never been explained: theories range from an accident to an al-Qaeda car bomb.
The fourth, a personal envoy of Osama bin Laden with alleged but unproven links to the 9/11 attacks on America, was blown up by a suicide bomber in Aleppo.