Usain Bolt began his bid to add a second Olympic 200 metres crown to his two 100m titles with a hugely comfortable heat victory today.

The Jamaican, who clocked an Olympic record 9.63 seconds to retain his 100m crown on Sunday, cruised to victory in 20.39secs.

Bolt has said he needs to win 200m gold again before he achieves his aim of becoming a "legend".