British title hope Jessica Ennis, a poster girl for the London Olympics, clocked the fastest ever time for a heptathlete in the 100m hurdles on the opening day of athletics on Friday. Ennis, the current world silver medallist, timed a scorching personal best and new British record of 12.54sec in brilliant sunshine in front of an 80,000-capacity crowd at the Olympic Stadium. To put her time into perspective, it was faster than American Kellie Wells\' victory in the 100m hurdles at last month\'s London Diamond League, in which the event\'s world champion Sally Pearson was beaten into second. It was the perfect start in the gruelling seven-discipline event for Ennis, with the high jump, shot put and 200m to come later in the day. Former world champion Ennis, who most recently won silver medals in the 2011 worlds in Daegu and world indoor pentathlon in Turkey in March, missed the Beijing Olympics through injury, and is under pressure to perform from an expectant public. The 26-year-old bagged 1,195 points for her hurdles, with Canadian Jessica Zelinka second in 12.65sec and American medal hopeful Hyleas Fountain third fastest in 12.70sec. Defending Olympic champion Natallia Dobrynska of Ukraine, who won the 2012 world indoor pentathlon title in a world record total just days before her husband and coach Dmytro Polyakov died, clocked a season\'s best of 13.57sec, more than 1.0sec and 155pts off Ennis. Russian world champion Tatyana Chernova only managed the 15th fastest time of 13.48sec to leave her 142 points adrift. The heptathlon concludes on Saturday after the long jump, javelin and 800m.