Yazidi women who refused to have sex with Isis fighters were burnt alive last year

When the young Yazidi saw his sister for sale online he barely recognised her. It had been 28 months since Dakhil last saw Hala and, though she was only 20, the face staring back at him from his mobile phone had been robbed of its youth.

“She was wearing black jeans and a blue T-shirt, but she looked so different, so old,” he recalled, scrolling through a list of young women featured in a secure members’ group on a social app used by Islamic State fighters to trade Yazidi slave girls.

Some seemed barely teenagers, facing the camera with tense, frightened smiles, wearing garish make-up and short skirts. Many were accompanied by an audio message in which a male voice gave details of their profile: