The idea came to screenwriter Matt Charman while waiting in his car at a red traffic light: a show whose two lead actors are handcuffed together. That moment led directly to Sky’s new six-part thriller Prisoner. “We were stopped next to a prison transport van, and one of my kids said: ‘Dad, what’s that?’,” explains Charman, who created and wrote the series with his production company, Binocular. “We drove away and the kids moved on to the next thing. But I found myself thinking: ‘Who’s in the back?