Michelle Perry, who a year ago finished as a distant also-ran in the Olympic Heptathlon, tonight claimed her first World title, winning a drama-packed 100 metres Hurdles final.

The 26-year-old American was always leading the race, in which the four principles - Perry, the Jamaicans Brigitte Foster-Hylton and Delloreen Ennis-London and Joanna Hayes, the Olympic champion - were drawn in the centre lanes.

But it was close, very close, through to the fourth flight, when Perry edged away slightly. You could sense the three others bristle in reaction.

Hayes then started to make a move, perceptibly closing the gap on her team mate. But then, at the penultimate barrier, when apparently poised to push past Perry, she clipped the hurdle. For a moment, it seemed as nothing.

But the loss of balance threw Hayes sideways. It may also have affected Foster-Hylton, the World silver medallist in Paris two years ago. And although she tried to correct her slip, Hayes had run out of space and painfully crashed through the last hurdle as her rivals sped away from her.

Perhaps it was the break in concentration at the vital moment, but the Jamaicans' attempt to catch Perry was as good as over once the American cleared the last hurdle herself and began to sprint for the line, which she crossed in 12.66sec to the Hyphenated Hurdlers' 12.76, with Ennis-London getting the judges' decision for silver.

Hayes had crossed the finishing line in 13.57, although the judges would disqualify her. She slumped on all fours, in pain as much as anguish at her fate, and needed to be helped away, heavy strapping and ice on her left knee.

Perry, who is coached by Bobby Kersee, has this year referred to "returning to my first love", the sprint hurdles, which had already seen her crowned as American champion. As the realisation dawned upon the Los Angeles resident that she was now also World champion, her delighted smile warmed the stoic crowd that had endured another uncomfortable night's weather in the Olympic Stadium.

Hyphenated hurdlers hurry through Helsinki hurricane

Perdita Felicien, the defending champion in the women's 100 metres hurdles, this time did not survive the semi-finals, as Jamaican and American sprint hurdlers took the upper hand ahead of Thursday's final.

The women sprint hurdlers had already had to endure some of the worst of the conditions on Tuesday night for their heats. Now, in the semi-finals, the steady rain made the semi-finals hazardous.

And with only the first two in each semi guaranteed to progress to the final, there was no margin for errors.

The high pressure saw Linda Ferga-Khodadin, the young Frenchwoman in the first semi-final, turn her ankle between the first and second flight and tumble painfully into the hurdle.

In the same semi, Felicien, of Canada, looked to be operating on a midrace skidpan, as she slid almost sideways in towards the eighth hurdle, losing vital ground, as Jamaica's Delloreen Ennis-London took first place in 12.79, with Mariya Koroteyeva, of Russia, second in 12.80. Sweden's Jenny Kallur was left to wait to find whether her PB 12.85 would be good enough. Felicien's 12.94 was not.

In the second semi-final, the Olympic champion also suffered defeat, Joanna Hayes beaten, 12.65 to 12.76 to Brigitte Foster-Hylton, the second of the hyphenated Jamaicans. At least Hayes ensured qualification with her runner-up slot.

Irina Shevchenko's 12.76 for third quickly confirmed Felicien's elimination, but Olena Krasovska, of Ukraine, like Kallur also clocking 12.85, for fourth in the second race, promised to complicate matters for the judges.

The pernicious wind changed direction, and velocity, between the last two semis, to the aid of those in the earlier races, because while Michelle Perry (USA), with 12.86, and Germany's Kirsten Bolm, in 12.95, were able to do enough to qualify automatically, those chasing them could not overcome the 3.3mps headwind to record fast enough times.

Kallur gets the eighth lane in the final over Krasovska on better finishing position.

Lightning fast heroines of Helsinki defy the storms

For Jeimy Bernardez, Glory Alozie, Barbara Rustignoli, Sarah Claxton, Mariya Koroteyeva, Virginia Powell, Delloreen Ennis-London and Flora Redoumi, their heat of the women's 100 metres Hurdles became something of a trial.

The eight women were lined up for the second heat of their event in the midst one of the heaviest torrential downpours ever witnessed at a major international athletics event.

The judges bowed to the elements. Such was the ferocity of the oncoming electrical storm, they had no other option. The eight women scuttled off for the shelter and protection of the ready room under the main stand, where they faced a two-hour wait before conditions had moderated sufficiently to allow the competition to re-commence, and their race to be staged.

When they re-emerged, after drying themselves off and warming up again, the skies were clearing, the track at least clear of the surface water.

In fact, the conditions were better than those encountered by the women who had run in the first heat, more than two hours earlier, when the American, Michelle Perry, had somehow despite the conditions managed to clock a 12.64sec winning time into a 2.1mps headwind, with Vonette Dixon (JAM) and Jenny Kallur (SWE) chasing her home in 12.95 and 12.96.

And so, after possibly the longest pause between a starter's "On your marks" and the firing of the gun, the second heat got underway, to be won by Ennis-London (JAM) in 12.65, with a 1.2mps following wind, while European champion Alozie (ESP) and Koroteyeva (RUS) both managed season's bests, 12.71 and 12.73 despite it all. The heat's fourth qualifier was Powell, in 12.91.

Now, normal service was resumed. Perdita Felicien, Canada's defending champion, took heat three in 12.77sec, while Brigitte Foster-Hylton, the runner-up two years ago in Paris, was the second Jamaican heat-winner in the event, taking the fourth heat in a barely wind-aided 12.64, equalling Perry for the fastest performance of the night.

The fifth and final heat brought forth the Olympic champion, Joanna Hayes (USA), who looked entirely unfazed by the delays and disruption, and cruised through to win in 12.79, shutting down off the last flight.

With the qualifying criteria seeing the first four in each heat and four fastest losers advance, it took at least a 13.00sec effort to proceed: Ireland's Derval O'Rourke running a season's best for sixth place in the third heat being the slowest of the fastest losers, who also include Yun Feng (CHN; 12.99), Anay Tejeda (CUB, 12.96) and Adrianna Lamalle (FRA, 12.93).