Usain Bolt has started his bid for an unprecedented second Olympic sprint double, cantering to victory in the opening round of the 200 metres.
Less than 48 hours after retaining his 100 metre crown in scintillating style, the towering Jamaican qualified for the semi-finals of his favourite event in a pedestrian 20.39 seconds.
Bolt's chief rival for gold, his compatriot and training partner Yohan Blake, also eased through in 20.38.
