Jamaica's Usain Bolt added the 200m crown to his Olympic 100m title in an incredible new world record time of 19.30 seconds in Beijing.

The 21-year-old, who won the 100m title in a world mark of 9.69 secs, powered past the field to cross the line and smash Michael Johnson's mark of 19.32.

Churandy Martina of Netherlands Antilles took silver with defending champion American Shawn Crawford third.

Great Britain's Christian Malcolm finished in sixth.

American Wallace Spearmon crossed the line second but was later disqualified for stepping out of his lane.