Doctor Foster

9PM, BBC1

This deliciously bitter drama just gets darker, as episode three finds Gemma (Suranne Jones, right) and Simon trying to establish what happened at the school. Why would Tom attack his best friend? With their son clearly disturbed by what’s happened between them, can his warring parents put their own feelings aside and work together to help him? Having instigated this uneasy new alliance, Gemma makes a show of practising what she preaches, while Simon struggles to play by the new rules. But can either of them really put their son first?