By Nick Mulvenney

LONDON (Reuters) - Britain's Jessica Ennis had a full house at the Olympic Stadium on its feet on Friday morning when she ran the fastest heptathlon 100 meters hurdles of all time on the first day of athletics at the London Games.

Running in the fifth and final heat in the first of seven events in the discipline, the former world champion stormed down the track towards the Olympic cauldron, which has been re-sited at the end of home straight.

Soaring across the hurdles in bright sunshine with the full-throated roar of the 80,000 crowd driving her on, the 26-year-old crossed the line in 12.54 seconds, the same time Dawn Harper ran to win 100 meters hurdles gold at the Beijing Olympics.

Ennis missed that Games four years ago because of injury and was looking for a good time in the hurdles, one of her best events, to kickstart her bid for gold.

Ukraine's Nataliya Dobrynska, the defending champion, won her heat convincingly in 13.57 seconds, while the other main contender for gold, Russia's world champion Tatyana Chernova, finished last in Ennis's heat in 13.48.

Ennis's run gave her 1,195 points to lead the rankings ahead of Canada's Jessica Zelinka (1,178) and American Hyleas Fountain (1,170), who also ran personal bests to finish second and third behind the Briton.

The heptathlon continues with the high jump, shot put and 200 meters on Friday before the long jump, javelin and 800m on Saturday.

(Editing by Ed Osmond)