In 2017 it will be exactly 50 years since a dapper Sidney Poitier announced to Rod Steiger, in the excellent film In The Heat of the Night: ‘They call me Mr Tibbs!’ Rod Steiger, playing a somewhat right-of-centre sheriff of a small town in Mississippi had hitherto been disposed to refer to Poitier — a senior policeman on his way home to Philadelphia — as ‘boy’, if you recall.