Like the ever-present mist on Daegu's mountains, a gloom lingered over the world athletics championships on Monday morning as the shock of Usain Bolt losing his 100 meters title sank in.

A victim of the one-false-start-and-you're-out rule, the world's fastest man was disqualified on Sunday night and his Jamaican understudy Yohan Blake crowned champion in a major anti-climax.

Athletics must swiftly come to terms with a perhaps overly harsh regulation which removed its biggest name from its blue riband race, and there will surely be plenty of soul-searching around whether the sport has shot itself in the foot.

Bolt, though, will be back for the 200 meters in which he also holds the world record. A command performance in that race will do much to put his toppling over the shorter distance in some context.

A hot Korean sun did its best to brighten the mood at the stadium and a 10,000 crowd of mostly schoolchildren settled in for a morning session of heats and qualifying.

Jessica Ennis did her best to give Britain some cheer after two of its big performers -- Christine Ohuruogu and Dwain Chambers -- were disqualified for false starts and 10,000m favorite Mo Farah was beaten into second.

The 25-year-old began her quest to retain her title in the heptathlon, but suffered her first defeat in a heptathlon high hurdles race since the 2006 European Championships.

En route to her world title in 2009, Ennis won her opening event, opening up a 76 points lead over the field which was never overhauled. She will have more to do this time round having been beaten first up by American Hyleas Fountain.

"I clattered a couple of hurdles which kind of knocked me off balance but I am fine -- I am used to hitting hurdles!" Ennis quipped. "I would have liked to run faster but 12.94 is still a good time."

Fountain then beat Ennis into second in the high jump, clearing 1.89 meters, with Ennis stuck on 1.86.

The American leads champion Ennis by 2,228 points to 2,187 after two events.

Britain's David Greene qualified fastest in the first round of the 400 meters hurdles in 48.52 seconds.

"I didn't want to expend too much energy in the heats," the Welshman said. "I didn't think it would be so fast but at the same time, I felt very conservative."

American Angelo Taylor was not fazed by the quick times, despite finishing only 12th fastest.

"They're pretty fast times but they got to come back and do it again tomorrow and in the final," he said. "I'm definitely the one with the experience," added the 2000 and 2008 Olympic champion.

Later on Monday the three fastest high hurdlers of all time take center stage. China's Liu Xiang has returned to form at exactly the right time and will fancy his chances of gold in the 110 hurdles.

The former world and Olympic champion is on a collision course with American David Oliver and 2008 Olympic gold medalist Dayron Robles.

Carmelita Jeter goes for gold in the women's 100, while Allyson Felix can achieve the first part of her double dream in the 400 final.

World titles are also at stake in the men's pole vault and hammer and women's shot put.