He might be referring to the old radio game, Mornington Crescent that aired on BBC Radio 4. Where all the rules are made up, but tensely debated none the less. One of my first website's was an attempt at an online game of Mornington Crescent.

> The game consists of each panellist in turn announcing a landmark or street, most often a tube station on the London Underground system. The aim is to be the first to announce "Mornington Crescent", a station on the Northern line. Interspersed with the turns is humorous discussion amongst the panellists and host regarding the rules and legality of each move, as well as the strategy the panellists are using.