Great Britain won a sixth gold in 48 hours to go fourth in the medal table on day seven of the London Olympics.
Steven Burke, Ed Clancy, Geraint Thomas
retained their men's team pursuit title in the Velodrome before
won the inaugural women's keirin with a thrilling sprint to the line.
The success took Britain's overall medal haul to 22, which is 14 better than at the same stage in Beijing four years ago.
The host nation now have eight golds, with only China, the United States and South Korea winning more.
Swimmer Rebecca Adlington had hoped to cap a remarkable day by holding onto her 800m freestyle title at the Aquatics Centre but she had to settle for bronze.
"I'm sorry I didn't get the gold that everyone expected me but it is so, so difficult," she said. "I hope they are proud of me for that bronze."
Three-time Olympic silver medallist
had taken rowing gold earlier in the day with
victory in the double sculls.
Grainger, who was overjoyed to finally win gold, said: "I feel this medal of all of them is the people's medal. "I feel so many people have been behind me and supported me and wanted this for me as much as I have."
Either side of that triumph at Eton Dorney, George Nash and Will Satch won a bronze in the
a result emulated by Alan Campbell
in the single sculls.
Britain's Karina Bryant, competing in her fourth Olympics,
added another bronze in the women's +78kg judo.
Jessica Ennis leads heptathlon after four events
Reflecting on her win, Pendleton said: "I can barely believe it right now. I really wanted to show what I could do and it worked out well."
In tennis, Andy Murray guaranteed himself at least a silver by beating Novak Djokovic 7-5 7-5 in the men's singles semi-final.
Murray will now meet Roger Federer in Sunday's Olympic final. For the Scot, it is an opportunity to avenge his defeat to Federer in last month's Wimbledon final.
Jessica Ennis began her bid for heptathlon gold in fine style,
breaking the British record for the 100m hurdles
with a time of 12.54 seconds at the Olympic Stadium.
"I still cannot believe I ran that time," she said. "Stepping into the stadium, the crowd really lifted me and got me that great time."
Her high jump of 1.86m kept her in front on 2,249 points but she slipped to second following the shot put.
A strong performance in the last event of the day - the 200m - took her back into the lead ahead of Saturday's final three events - the long jump, javelin and 800m.
Grainger and Watkins win gold for GB
Prime Minister David Cameron joined other athletes at the Great Britain team headquarters to watch Grainger and Watkins win at Eton Dorney.
"It was emphatic and an absolutely brilliant performance by Katherine and Anna, a privilege to watch it here at GB House and another gold medal," he said. "We're really doing some good stuff here."
On Thursday, Britain enjoyed one of its best days of any Olympic Games, winning three gold medals and three silvers.
The men's sprint cycling team twice broke the world record
on their way to victory
in a packed Velodrome, a result that meant Sir Chris Hoy equalled Sir Steve Redgrave's British record of five Olympic golds.
Gold also came from the canoe slalom pair of Tim Baillie and Etienne Stott, followed minutes later by shooter Peter Wilson's triumph
in the men's trap.