The first few minutes of Showtrial (BBC One) are mildly disorientating. The new five-episode courtroom drama has lots of grand themes – class, prejudice, corruption, the justice system – and doesn’t muck about before plunging us into things. After a university ball, a student, Hannah Ellis (Abra Thompson), goes missing. The only clue to what might have happened is a series of unpleasant text...