Organisers may think the most closely-guarded secret of the 2012 Games is who will light the Olympic flame, but of far greater interest to the wider sporting public is the condition of Usain Bolt's right hamstring.
The Jamaican triple gold medallist from Beijing is the number one attraction of the London Games, but the question mark over his fitness has added an extra layer of intrigue to what is already an eye-wateringly exciting 100 metres race.