Alongside the humanitarian fall-out from Turkey's invasion of northern Syria there are grave security concerns. Not least what will happen to the thousands of so-called Islamic State militants imprisoned by Syrian Kurdish forces? John Letts and Sally Lane are the parents of one such prisoner, British born Jack Letts. He left the UK in 2014 to live in the so called IS Caliphate. Since then he's had his British citizenship revoked and his parents have been convicted under UK anti-terror laws for sending him money. What will become - what should become - of Jack Letts? Show less