Victoria Pendleton capped a sensational evening for Britain's track cyclists with victory in the women's keirin.
Pendleton delighted with gold
The 31-year-old Briton, who
after London 2012, adds a second gold to the one she won
in the sprint at the Beijing Games in 2008.
Pendleton hit the front at the bell and held off a late charge from China's Guo Shuang, with Hong Kong's Wai Sze Lee a surprise bronze medallist.
"I can barely believe it right now," Pendleton said.
"Thank you so much to everyone who's helped me get here. The crowd have been fantastic and it really helped me today."
Australia's Anna Meares, the pre-race favourite, could only finish fifth.
The race - a frenetic affair that starts with the riders following a small motorbike for five-and-a-half laps before being released to sprint the final 625 metres - came only half an hour after the
British men's pursuit quartet
claimed gold in a new world record.
2012 track cycling golds
Britain have won seven out of 10 track cycling gold medals at the London 2012 Olympics
And that superlative performance followed another world record display
by the women's pursuit team
in their qualifying round.
By the time the six riders in the last race of the evening took to the track, the noise was deafening.
Not that this race needed much of a build-up.
Meares v Pendleton was one of the most eagerly anticipated contests coming into these Games, with the 28-year-old Queenslander expected to get the better of her British rival in the keirin, an event she has won at the last two World Championships.
But Pendleton looked in great form during her ultimately fruitless rides
in Thursday's team sprint competition.
The Bedfordshire-born star was disqualified from the event, with partner Jess Varnish, when Pendleton slightly mistimed a changeover.
Pendleton in tears collecting her medal
The raw speed she exhibited, however, was noticeable, and expectations of a keirin classic grew when both Meares and Pendleton were comfortable winners of their semi-finals.
But British cycling's glamour girl blew her rival away in the final with a burst down the back straight that catapulted her from fourth to first with 250m to ride.
Guo pushed hard but there was no getting around Pendleton, who now looks to have an excellent chance of finishing her career with another gold medal in the women's sprint, which starts on Sunday.
She has won six world titles in that event, as well as her 2008 Olympic crown.