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

While Bolt's win was never in doubt the minor medals were shuffled twice, first when American Wallace Spearmon was disqualified for running out of his lane and denied bronze.

Initially, Churandy Martina of Curacao (Netherlands Antilles) took silver.

Then officials upheld the US team's protest that second-placed Martina had also stepped out of his lane which bumped Crawford into silver and Dix, the 100m bronze medallist, up to third.

Defending champion American Shawn Crawford was then placed third.

Within minutes of the Bolt second golden victory, his fellow Jamaican .... Walker took gold in the women's 400m hurdles.

Backgrounder on Jamaica's homegrown champions programme

Bolt has absolutely decimated all before him - has he now changed sprinting?

American Wallace Spearmon had crossed the line in the bronze medal position but was later disqualified for stepping out of his lane.

"A dream come true"

Bolt told the BBC after his sensational win: "It's great. I have a great feeling.

"This is a dream come true. You come out every day to be a champion and I'm just happy."

When asked if he planned to go all out for Johnson's world record, the 21-year-old said: "I was worried after the semis.

"But I told everybody I would leave everything on the track and I did just that.

"I've proved I'm a true champion and that with hard work anything is possible."

Jamaica is so small. Everybody should be happy and I'm happy too.   Melanie Walker, womens 400m hurdles gold medallist

Bolt had been accused of jogging through the line in his heats but the Jamaican said 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.

Women's gold

Right after the men's 200m, Jamaica's Melaine Walker broke the Olympic record to win gold in the women's 400m hurdles.

	Melanie Walker took Jamaica's fourth gold

Walker was in a battle with American Sheena Tosta for the first part of the race before breaking clear to cross the line in 52.64 seconds.

Walker was delighted with her gold-medal winning performance.

"I wanted to be victorious," she told BBC Sport. "Jamaica is so small. Everybody should be happy and I'm happy too."

Carl Lewis

Bolt accelerated away down the straight, gritting his teeth as he chased down gold and the record that Johnson set 12 years ago in Atlanta.

Bolt seized both with ease, becoming the first man to secure the prestigious Olympic sprint double since Carl Lewis in 1984.

The 6ft 5in sprinter is also the first since compatriot Don Quarrie in 1976 to hold both sprint world records at the same time.

Bolt, who will celebrate his 22nd birthday in Beijing on Thursday, could win a third gold medal when he competes in the 4x100m relay.