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 19.32s.

The 21-year-old, who turns 22 tomorrow, made a brilliant start and was already well clear of the field coming into the 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 to 19.30s.

Churandy Martina, of the Dutch Antilles, took silver in 19.82.

American Wallace Spearmon crossed the line in third place in 19.95 but was disqualified for running out of his lane and team-mate Shawn Crawford, who ran 19.96 was promoted to the bronze medal.

Britain's Christian Malcolm finished seventh in 20.40.

When Bolt set off on his lap of honour 'happy birthday' rang out over the tannoy.

Earlier in the day, Keri-Anne Payne, Cassie Patten and Bryony Shaw boosted Britain's hopes of a top four place in the medals table by adding three more medals to the Team GB tally in Beijing today.

Payne and Patten took silver and bronze respectively in the open water 10km swimming and Shaw weighed in with a bronze in sailing's RS:X windsurfing class.

The overall British medal tally now stands at 36 keeping Team GB ahead of Australia in what is expected to become a battle for fourth spot.

Britain, with 16 golds and 36 medals overall, still occupy third place in the medal table, but Russia are coming up on the rails and, with a number of key team events to be decided as the Games draw to a close, may overhaul Britain.

Australia, who have 11 golds, were facing the possibility of a day without adding to their medal tally and Britain have now overtaken them in number of medals won after today's haul.

Payne and Patten's medals drew Britain level on 35 and Shaw's bronze edged them ahead.

There were just 11 medals up for grabs on the 12th day of competition in Beijing - the second fewest of any day in the entire Games.

And Australian athletes had just one chance in the remaining events to avoid a day without a medal with Ryan Carneli hoping for a repechage spot in the men's -58kg taekwondo event.

There was disappointment for Wakefield's 200m runner Emily Freeman, however, who finished well down the field in her semi-final heat and will not run in the final.

Gold medal hopeful Shanaze Reade overcame an early scare at the BMX biking before recording the second fastest time in the seeding round.

The 20-year-old fell at the first corner on her first run, trailing in with the slowest time and appearing to suffer an arm injury.

But she picked herself up to record a time of 36.882 seconds to ensure she is in the second run of quarter-final races.

But men's competitor Liam Phillips failed to reach the semi-finals with his quarter-final already over before Reade's begins this afternoon.

Britain's first Taekwondo competitor Michael Harvey suffered a gallant defeat to world silver medallist Guillermo Perez.

The Manchester teenager trailed 2-0 to the Mexican but fought back to 2-2 in the men's -58kg bout to force a sudden death overtime round.

And despite briefly believing he had scored the winning point, the judges scored for the Mexican, meaning Harvey must hope Perez advances all the way to the final in order to get a second chance in this evening's repechage.

Harvey said: "I caught his pad but obviously it wasn't hard enough or the judges missed it. I thought I had a good chance going into that last round but obviously it didn't go the right way.

"I did well because I was up against the world silver medallist but he was there to be beaten and I'm a bit gutted that I've lost. It's great experience for London 2012 but I wanted to go a bit further."