Jamaica's Usain Bolt was overwhelmed after becoming the first man to win the Olympic sprint double for 24 years with his second amazing world record in five days in Beijing.
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 thankfully no doubt about the winner, Bolt becoming the first man since Carl Lewis in Los Angeles to win the 100 and 200m titles.
Bolt, who turns 22 on Thursday, 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 19.31s, 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."
Britain's Christian Malcolm, who finished seventh in the race before being elevated to fifth following the 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," he 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 on the track, Jamaica's Melaine Walker won gold in the 400m hurdles in a new Olympic record of 52.64s.
Walker powered off the final hurdle to finish comfortably ahead of American Sheena Tosta with Britain's Natasha Danvers putting an injury-plagued season behind her to snatch bronze.
"I was kind of expecting it," Walker said. "I've dreamed about it a million times. I see my race over and over and I can see myself crossing the finish line."
The first gold medal of the evening went to Aksana Miankova of Belarus after a throw of 76.34m gave her the women's hammer title and new Olympic record.
Cuba's Yipsi Moreno, runner-up in Athens in 2004, again had to settle for the silver medal after a best effort of 75.20m, while China's Zhang Wenxiu delighted another 90,000-strong crowd by claiming bronze with a throw of 74.32m.
"This is my first gold medal, I felt I was so successful