Each series seems to be based rather narrowly on a fairly fixed formula of the 'famous three' in pursuit of a 'bent' senior cop. I accept that this formula can deliver a high level of tension, but it runs the risk of becoming boring and consequently trying to generate excitement by means that don't always seem credible. I prefer Morse, Endeavour, Foyle and Cassie where the action is less frenetic but the context is always well developed, the 'bad uns' show a wider range of personal, social and professional characteristics and the central characters come across convincingly as human beings whose interests in life and idiosyncrasies are central to each plot