Thomas Boswell, the American sportswriter, called one of his books Why Time Begins on Opening Day, which neatly grasped the truth that certain moments in the sporting year are inherently dramatic.

Rugby union reaches its own opening day this weekend. While followers look forward to the later stages of the Heineken Cup, this summer's Lions tour and beyond them to the 2011 World Cup, the RBS Six Nations Championship remains the fulcrum on which the season turns.