Victoria Pendleton was denied a fairytale farewell on the track as she lost her Olympic sprint title to Australia's Anna Meares.
Tears flow for emotional Pendleton
Pendleton won race one of the three-leg final against Australia's Meares by 0.001 seconds but was disqualified for riding out of the sprinting lane.
The Briton - the defending champion - tried to hit back in race two.
But a stunning Meares finish gave her a 2-0 win and left Pendleton with silver.
Guo Shuang of China took bronze after beating Germany's Kristina Vogel 2-0.
"I would have loved to have won on my final race, but I'm just so glad that's it all done and I can move on," said Pendleton."
Laura Trott winning gold in the omnium
Sir Chris Hoy defending his keirin title,
Britain end with seven golds, one silver and a bronze to show for six days in the velodrome.
2012 track cycling golds
Britain have won seven out of 10 track cycling gold medals at the London 2012 Olympics
Defeat by her fiercest rival was an unhappy end to Pendleton's illustrious career on the track, but the six-time sprint world champion has the consolation of
taking keirin gold
away from London 2012.
Meares, in contrast, came into the final with only a bronze from the team sprint to her name at London 2012, but the 28-year-old left with Australia's first gold medal in the velodrome of these Games.
The two riders have enjoyed some epic duels on the track in the past and their first cat-and-mouse encounter did not disappoint.
Meares stalked Pendleton like a tiger around the track and won the first race after the British rider was adjudged to have come out of her lane as she held off the Australian by the width of a tyre.
That left Meares needing just one more win to take gold, which she sealed with a burst of speed on the final bend that left Pendleton unable to respond.
"There was no disputing that final race. Anna Meares was just the better sprinter. We have to hand it to her, it was a great race but it's disappointing for Victoria Pendleton. I don't think Anna thought she could win judging by the look on her face at the end. She looked surprised. Meares was just stronger and she knew she had it on that final bend."
Tears followed from an emotional Pendleton, whose dream of becoming the first British woman to win three Olympic golds was dashed.
However, her two golds mean she remains alongside runner Kelly Holmes, swimmer Rebecca Adlington, fellow track cyclist Trott and sailors Sarah Webb, Sarah Ayton and Shirley Robertson as the country's most successful female Olympians.
Meares, meanwhile, was left to celebrate her second Olympic gold medal, eight years after she won her first in the 500m time trial in Sydney.
"Victoria's such a hard-fought opponent and she's dominated the sport for so long," said Meares. "It's been such a difficult challenge and to be able to win the Olympic title for me, it's so special."