US swimmer Michael Phelps poses with the gold medal
Michael Phelps bowed out of swimming with a final flourish on Saturday as poster-girl Jessica Ennis crowned one of British sport's most memorable days with the London Games' signature moment.
As Usain Bolt and Yohan Blake made their first appearance on the track, Phelps left clutching his 18th gold -- and 22nd medal overall -- after the 4x100m medley relay, the climax to races in the Aquatics Centre pool.
But the night's biggest roars were reserved for Ennis, who confirmed heptathlon gold with a surging 800m win that raised the 80,000-capacity Olympic Stadium crowd in a spine-tingling ovation.
Her victory was the highlight of a spectacular day eight for the hosts, who won six golds -- their most on a single day of Olympic competition for more than 100 years.
"I'm just so chuffed, I can't believe it," said the tearful Ennis. "After the javelin I knew I was in for a good score but I couldn't let myself believe it until I crossed the finish line."
As Ennis basked in the stadium applause, Britain's Greg Rutherford was a surprise winner in the long jump. And Mo Farah then sent the crowd into delirium when he won the men's 10,000m.
"It's never going to get better than this, this is the best moment of my life," said Farah.
Thanks to the triple haul -- Britain's most on one day of Olympic athletics -- and wins in rowing and cycling, the home team finished the day third on the medals table on 14 golds, behind the United States (26) and China (25).
"Our finest Olympic hour" was the headline in The Sunday Times, while The Sun tabloid called the gold-medallists, "The Six Pack".
In the pool relay, "Baltimore Bullet" Phelps, swimming the butterfly leg, made up more than half-a-second over his second 50m as he reeled in leaders Japan. Nathan Adrian finished the job with an explosive freestyle close.
The race ended the greatest swimming career in Olympic history, after Phelps' unmatched eight gold medals at Beijing 2008. In London, he outstripped Soviet gymnast Larisa Latynina as the most decorated Olympian.
"It's tough to put into words right now," Phelps said. "I did everything I wanted to do."
Earlier, Sun Yang took more than three seconds off his own 1500m world record to seal China's fifth swimming gold -- making it their best Olympics in the pool.
Sun, who flirted with a shock disqualification when he dived in well before the rest of the field, smashed the water repeatedly and cried tears of joy after the race, before getting out and bowing to the stands.
Dutch speedster Ranomi Kromowidjojo completed a sprint double with victory in the women's 50m freestyle, and Missy Franklin led the United States to a 4x100m medley gold in a world record time of 3min 52.05sec.
The win meant the United States finished the pool events with 16 swimming golds, including four for the 17-year-old Franklin, their newest superstar.
South Africa's Oscar Pistorius became the first double amputee to compete in Olympic track athletics as he sprinted into the 400m semis on his specially made, carbon-fibre blades.
"It's just an experience to be here. It's a dream come true," said Pistorius.
Defending 100m champion Bolt clocked 10.09sec in his first round heat for the blue riband event of the Games while Jamaican compatriot Blake timed 10sec.
However, both men were upstaged in front of 80,000 people at the Olympic Stadium by the 9.88sec run by America's Ryan Bailey.
"I expected it, I'm running well, I'm happy, training is great. Reaction was good," said Bolt, whose build-up to the Games had been hit by a number of worrying niggles.
Meanwhile, Serena Williams won the 'Golden Slam' -- all four Grand Slam titles, plus Olympic gold -- with a thumping 6-0, 6-1 win over Maria Sharapova. She will also play Sunday's women's doubles final with her sister Venus.
Britain won two more rowing titles, and also smashed the women's team pursuit cycling world record -- for the third time this week -- to claim their fourth gold out of five so far in the Velodrome.
In badminton, Li Xuerui took the women's singles title before Chinese compariots Zhao Yunlei and Tian Qing claimed the women's doubles.
And in the day's final event, Jamaica's Shelly-Ann Fraser-Pryce retained her women's 100m title in 10.75sec, 0.03sec ahead of a lunging Carmelita Jeter.