Usain Bolt's glittering career swansong came crashing down when he pulled up with a leg cramp on the anchor leg of the world 4x100m relay won by Great Britain. There was high drama in Saturday's relay as anchor man Bolt received the baton in third place behind eventual gold medallists and runners-up America. Less than 50 metres down the track, Bolt suddenly pulled up, clutching his left leg, tumbling to the track with what was later diagnosed as a hamstring cramp. (Video Credit: SNTV)