The 100m hurdles, got under way shortly after 10am, with Ennis making her Olympic debut.

Sheffield's Jessica Ennis made a sensational start in her bid for heptathlon glory in front of a massive crowd for the opening of the athletics in the Olympic Stadium.

Only a handful of seats in the 80,000-capacity stadium were empty when the first heptathlon event, the 100m hurdles, got under way shortly after 10am, with Ennis making her Olympic debut in the fifth and final heat.

The 26-year-old broke the British record and smashed her personal best with a stunning time of 12.54 seconds that left the Sheffield athlete shaking her head in disbelief.

The time was 0.02secs quicker than the previous national record set by hurdles specialist Tiffany Porter, and gave Ennis1,195 points for a lead of 17 from Canada's Jessica Zelinka.

British team-mates Louise Hazel and Katarina Johnson-Thompson were in joint 15th place after both clocked 13.48s in their heats, Hazel setting a season's best and Johnson-Thompson, the world junior champion in the long jump, equalling her personal best.

As well as leading the competition, Ennis - who had taken a quarter of a second off her personal best - had opened up a welcome gap on her main rivals for the gold medal.

Russia's Tatyana Chernova, who deposed Ennis as world champion last year, was 142 points behind after clocking 13.48, with defending Olympic champion Nataliya Dobrynska 155 adrift after running 13.57.

Ennis carried her fine form on to the next event, the high-jump, producing a jump of 1.86 metres which confirmed her lead after the morning session, with a score of 2249.

There was more good news for Britain in the women's triple jump, with 39 year-old Yamile Aldama reaching the final with her first jump in qualifying of 14.45m.

In the men's shot, Carl Myerscough failed to reach the final after finishing 29th in qualifying with a best of 18.95m, more than a metre down on his season's best.