The number 10 in rugby is arguably the most important player on the pitch. They are the master tactician and the playmaker, the goal kicker and the person who calls the shots. The number 10 shirt carries responsibility, respect and a sense of prestige and the pressure is intense both on and off the pitch. It's the Irish fascination with the selection of who should wear the number 10 shirt which has produced great debate across the decades and created some of the most intense rivalries in world sport, such as that between Ollie Campbell and Tony Ward or Ronan O'Gara and David Humphreys.