* Record-breaking Phelps seeks medal number 21 *
A packed Olympic Stadium took centre stage on Friday with the opening day of the athletics when home favourite heptathlete Jessica Ennis thrilled the raucous crowd with a world best time in the 100 metres hurdles event.
Business was not quite done in the pool, where American swimmer Michael Phelps – the most decorated Olympian of all time with 20 medals including 16 golds – will race his last individual Games event in the final of the 100 butterfly.
And on the seventh day of full sporting competition at the London Games, the cycling velodrome promised more British glory in the men's team pursuit and women's keirin.
Britain's men took cycling track team sprint gold on Thursday, but the taste of victory was soured when German-born rider Philip Hindes admitted to falling over on his bike on purpose in the heats to avoid being disqualified.
It also raised uncomfortable questions about gamesmanship at the Games, after eight badminton players were thrown out for deliberately losing matches to manipulate the draw, breaking the spirit, but not the rules of their sport.
The home nation has stormed up the medals table and a rowing win for Katherine Grainger and Anna Watkins before 25,000 ecstatic fans at Dorney Lake in the women's double sculls made it six golds and fourth place overall.
Ennis, the London Games poster girl whose every move was greeted with deafening roars at the 80,000-capacity stadium, will hope to add to that tally after setting a world best time for a heptathlete in the 100 metres hurdles.
World champion Vivian Cheruiyot of Kenya begins her bid for a distance double in a much-anticipated 10,000 final where Ethiopian Olympic champion Tirunesh Dibaba, who has the fastest time of the year, is expected to be her main rival.
Cheruiyot also has her eye on the 5,000 next week as she attempts to replicate her double gold from last year's world championships.
Elsewhere in track and field, a trio of Americans will seek to capture the men's shot put gold for United States for the first time since 1996.
Reese Hoffa, Ryan Whiting and Christian Cantwell, silver medallist in Beijing four years ago, set out to dethrone Olympic champion Tomasz Majewski of Poland with Germany's world title holder David Storl also likely to be in strong contention.
With the opening of the athletics, the jewel in the Olympic crown, excitement has begun to build towards Jamaican Usain Bolt's defence of his 100 title on Sunday and his 200 crown four days later.
PHELPS PHENOMENON
In their final duel before Phelps is due to retire, he pushed fellow American and world champion Ryan Lochte into second place on Thursday to become the first male swimmer to win the same individual event three times at successive Games.
Missy Franklin, 17, chases her third gold medal in the 200 backstroke while Rebecca Adlington carries British hopes in the 800 freestyle, bidding to repeat a victory in Beijing.
United States also celebrated victories on Thursday in the women's rowing eight and for 16-year-old Gabby Douglas in the all-around gymnastics where she edged out Russian Victoria Komova who was too upset to wear her silver medal.
She helped the United States catch up with the Chinese in the overall medal standings, with both countries on 18 golds on day seven of full competition.
ROWING GOLDS
In the scandal over match-throwing in the badminton tournament, disqualified Chinese Yu Yang announced she was quitting the sport.
She was one of eight women, two each from China and Indonesia and four from South Korea, kicked out of the Games for playing to lose group matches in order to secure easier knockout opposition.
In the rowing on Friday, Britain's Grainger won her gold at the fourth time of asking following three silver medals at the last three Games.
New Zealand struck gold twice, with Mahe Drysdale taking the men's single sculls and men's pair Eric Murray and Hamish Bond cruising to victory in comprehensive fashion.
Germany powered to gold in the men's quad sculls, finally getting their revenge on the young Croatian crew who had beaten them all season.
But another German rower, Nadja Drygalla, who has already finished competing at the Games, voluntarily left the Olympic village following reports that her boyfriend was a far-right extremist.
Sergei Martynov, the 44-year-old Belarussian, used a 13-year-old gun and bullets from the Soviet era to win the men's 50 metre prone rifle with a world record score.
And at Wimbledon, Roger Federer of Switzerland remained on course to repeat his heroics in the Grand Slam in July, beating Argentina's Juan Martin del Potro in a marathon 19-17 third and final set for a place in the final.
