American football is one of the most intricate, subtle games in the world, a fact sometimes obscured by the violence and apparent mayhem unfolding on the pitch. There is order in this chaos, and the shots are being called by the coach.

Whether the coach adopts the cool, inscrutable demeanour of the Dallas Cowboys' Tom Landry (in charge between 1960 and 1988), or the less restrained emotionalism of the Chicago Bears' Mike Ditka (1982-92), every good coach has a playbook, a guide to the ingenious or simple "plays" (manoeuvres) he wants the team to carry out.