ITV has a decent track record in “social purpose drama” – see last year’s take on the 1989 Hillsborough disaster . Carolyn McCall, chief executive of ITV, will doubtless be delighted at the wide-ranging political impact of the broadcaster’s hit drama Mr Bates vs the Post Office . The Bates drama pulled in 4 million viewers an episode when it was shown, and a further 10 million through ITVX .