Britain'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 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, who missed the Beijing Games after suffering a career-threatening foot injury, considers the hurdles her strongest event and is actually entered for the individual event in London as a back-up.

But there were no signs of plan B being required after Ennis 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 Ennis 1,195 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.

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.