For the first time since the advent of electronic timing, the field for the blue riband event of the Games will comprise the four fastest men in history -- champion Usain Bolt, Yohan Blake, Asafa Powell and Tyson Gay.

Bolt rewrote the record books at the 2008 Beijing Games with a dazzling sprint double that turned logic on its head and forced a recalibration of what had previously been thought humanly possible.