On a dingy estate in St Petersburg Stacey Dooley sits around a kitchen table with three Russian sex workers. A security guard stands by the door, ushering in clients – often three or four at a time. Single beds are cordoned off with ragged curtains.

“Sometimes they want a gangbang”, one of them tells Stacey. “And sometimes groups of men come ­carrying weapons...”

Dangerous environments are all in a day’s work for documentary-maker Stacey Dooley, but her new three-part series takes her into the darkest corners of global