The man stands furtively on a street corner, his face masked by a hoodie, his tense eyes scanning the crowd for any hint of Islamic State militants.

He was one of them before he left Syria a year ago, and he is afraid.

Now he chain-smokes as he describes the indiscriminate killing, the abuse of female recruits, the discomfort of a life where meals were little more than bread and cheese or oil. He recounts the knife held to his throat by fellow fighters who demanded he recite a particular Quranic verse on Islamic warfare to prove himself.