The Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group is on the retreat in Syria and Iraq, where their two main bases were located. But what will happen to the thousands of foreigners, including some from the United Kingdom, who have travelled to fight or support its cause? The group has boasted of its involvement in attacks on British soil, as well as other European countries. So how should those who do return to the UK be treated?
Al Jazeera's Barnaby Phillips reports from London.