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Britain's Jessica Ennis ran a heptathlon record 12.54 seconds in the 100m hurdles to get her quest for Olympic gold off to the perfect start.
Ennis's time also broke the British record, equalling American Dawn Harper's winning time in the individual event at the 2008 Beijing Olympics.
It was a new personal best by 0.25 secs, meaning Ennis leads the standings after the first of the seven events.
Her main rival, reigning world champion Tatyana Chernova, is 15th overall.

Analysis

Image of Tom FordyceTom FordyceBBC's Chief sports writer in the Olympic Stadium
Phenomenal hurdling from Jess Ennis and a phenomenal response from the 80,000-strong partisan crowd to match. While all had hoped for a strong start in one of Ennis's best events, no-one had dared dream that she might knock a quarter of a second off her personal best. The pressure on her must have been immense - those of us watching in the stands felt anxious enough - but she delivered fantastically.
Ennis's 1,195 points put her 142 points clear of the Russian, when their previous PBs suggested a gap of almost half that.
The Sheffield athlete's display was the fastest ever 100m hurdles race from a heptathlete and was greeted with deafening noise from the 80,000 crowd in a packed Olympic Stadium.
It also broke hurdles specialist Tiffany Porter's British record by 0.02 secs.
Conditions were almost ideal for the multi-eventers, and a 12.65 from Jessica Zelinka and 12.70 from Hyleas Fountain put them second and third overall on 1,178 and 1,170 points.
Ukraine's Nataliya Dobrynska, the reigning Olympic champion, produced a season's best of 13.57 secs to lie 22nd with 1,040 points.
Commonwealth champion, Britain's Louise Hazel, ran 13.48 secs in her heat while her 19-year-old compatriot Katarina Johnson-Thompson - newly crowned world junior long jump champion - began the biggest competition of her life with a fine 13.48 to equal her personal best.
The second of the seven disciplines is the high jump which starts at 11:15 BST. The shot put follows at 19:00 before the 200m at 20:45 which rounds off the opening day of competition.
On Saturday, the athletes return for the final three events, the long jump, javelin and 800m.
World 400m hurdles champion Dai Greene moved safely through his heat on a good first morning for Britain's athletes.
His fellow medal contenders Yamile Aldama and Christine Ohuruogualso progressed as the packed stadium created a wonderful atmosphere for the home athletes.
Greene made light of a tricky draw in lane one to win the third heat in a comfortable 48.98 secs, and will be joined in Saturday's semi-finals by current world number one Javier Culson and reigning Olympic champion Angelo Taylor.
Jack Green and Rhys Williams will also join Greene after coming through their heats in contrasting fashion.
Green, who trains with world champion Greene in Bath under the legendary Malcolm Arnold, came through strongly to qualify automatically in second from his heat while Williams - drawn in a stacked heat - made it through as a fastest loser.
Ohuruogu ran a typically well-judged race to take second behind the Francena McCorony of the United States in 50.80 secs, although the fact she let the lead slip may give her a slightly worse lane draw in Saturday's semis.
Her main rival Sanya Richards-Ross breezed through as winner of the fourth heat despite a sudden rain shower leaving the track covered in puddles.
The 40-year-old Aldama, who went straight into Sunday's triple jump final with her first effort of 14.45m, spoke for many when she said afterwards: "This is my fifth Olympics and I've never experienced a crowd like this in the qualifying round."
Britons Shana Cox and Lee McConnell both went through to the 400m semis, finishing third in their heats.
But there was disappointment for Carl Myerscough, who went out in shot put qualifying with his best of 18.95m placing him just 29th - well outside the top 12 required.