Bolt, who casually shaved 0.03 seconds off his own record in winning the 100 metres title in sensational style on Saturday, clocked 19.30secs to break Michael Johnson's 12-year-old record of 19.32secs.

Churandy Martina of the Dutch Antilles and American Wallace Spearmon were initially credited with silver and bronze, only to both be disqualified for running outside their lanes.

That gifted American Shawn Crawford the silver medal with team-mate Walter Dix claiming bronze.

There was never any doubt about the winner, Bolt becoming the first man since Carl Lewis in Los Angeles to win the 100 and 200m titles at the same Games.

The 21-year-old, who turns 22 today, made a brilliant start and was already well clear of the field coming into the home straight.

But unlike the 100m final, where he began celebrating well before the line, this time he sprinted through the tape to initially stop the clock at 19.31, a time that was swiftly rounded down.

"This is more than I can handle really, I'm a bit overwhelmed," Bolt said. "I didn't think a 200m record was on because I felt tired after the heats.

"But I told everyone I was going to come out here and leave everything on the track and I did just that.

"I've proved I'm a true champion and that you can do anything you want with hard work. It's great. I have a great feeling. This is a dream come true.

"You come out here every day as an athlete to be a champion and this is just more than I can handle.

"It means a lot to me and I know it means a lot to the country also. I spoke to the PM (of Jamaica) and he told me everyone is dancing in the streets. I have written history. I am happy with myself and real proud.

"I told myself if I was to get the world record it would be here because it is a fast track.

"Everything came together and I just blew my mind and blew the world's mind.

"I have been saying all season that the 200m means a lot more than the 100m. The world record means a lot because I have been dreaming of this since I was so high.

"I was the youngest ever junior world champion and from that moment the 200m has meant a lot to me."

Britain's Christian Malcolm, who finished seventh in the race before being elevated to fifth following the two disqualifications, paid tribute to Bolt.

"You could tell by the way he ran the 100m that he was always going to be capable of breaking the world record," Malcolm said.

"He is without a doubt one of the best competitors I have ever seen. He has raised the bar now and the rest of us have got to follow. It is amazing, what can you say?

"I think people were shocked when Michael Johnson did what he did in Atlanta but I think people will be more shocked by what Usain Bolt has done in these championships.

"He is a good guy and it can only help the sport."

Elsewhere, it was another productive day for medals for Great Britain, who were able to maintain their position of third in the medals table behind leaders China and the USA.

Natasha Danvers claimed bronze in the 400m hurdles to boost Britain's bid for a top-four finish.

Swimmers Keri-Anne Payne and Cassie Patten launched yesterday's medals haul with silver and bronze in the open water event, before Bryony Shaw won bronze in the windsurfing RS:X competition.

Payne and Patten set the pace throughout the 10,000m race, and were only overhauled in the final 750m by Russian world champion Larisa Ilchenko, who beat Payne by just one-and-a-half seconds to claim gold.

Patten held on for third to ensure that after 24 years without a single swimming medal, British women have now collected five in one Games.

"Your body is saying stop but your head is saying come on keep going," said Patten. "The last kilometre felt like 20km, every time I looked up the finish seemed no closer."

Shaw earned her medal – GB's fifth from the sailing regatta at Qingdao – by finishing second in the medal race.

She was briefly in the gold medal position in the race but had to settle for bronze.

"I came here wanting a medal and I knew that I had the ability," said Shaw.