Usain Bolt added the 200m crown to his Olympic 100m title in a new world record time of 19.30

The 21-year-old,who turns 22 on Thursday 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 clocked 20.40 secs for sixth place. American Wallace Spearmon had crossed the line second but was later disqualified for stepping out of his lane.

Bolt had been accused of jogging through the line in his heats but the Jamaican promised he would run flat out in the final and he delivered on that promise with interest. He blasted out of the blocks and was already well clear of the field going into the bend at the Bird's Nest stadium.  

Usain Bolt celebrates after breaking the 200m world record

The Olympic 100m champion accelerated away down the straight, gritting his teeth as he chased down gold and Johnson's record that he set 12 years ago in Atlanta. Bolt seized the gold and the record with ease, becoming the first men to secure the prestigious Olympic sprint double since Carl Lewis in 1984.  

He follows compatriot Don Quarrie as the first man since Quarrie in 1976 to hold both sprint world records at the same time. The sprinter is set to celebrate his 22nd birthday in Beijing on Thursday by beginning his quest for a third Olympic gold in the men's 4x100m relay heats.

Welshman Christian Malcolm was satisfied with his achievement in the 200m final after finally rediscovering some form after a spate of injuries. "I didn't run particularly great," the 28-year-old said. "But I have got to take the good from these championships.

"I have made the final and I am injury free, so I can move on and build from this. "You have got to keep going because he [Bolt] is going to have bad day sometime. He has had a great championships and got it right on the day but I am improving so I am looking forward to next season."