Greene looks good as he does Bolt impression

Britain's Dai Greene impressed in winning his 400m hurdles semi-final yesterday (PA)

Just as another golden hope turned into a silver lining for the Great Britain team in Daegu yesterday, the glint of a possible Midas touch came into view. It remains to be seen whether Dai Greene will succeed where Mo Farah and Jessica Ennis have failed and win gold at the World Championships in South Korea. In emerging from his 400m hurdles semi-final as a comfortable winner yesterday, though, the Swansea Harrier showed the assurance of a contender who is going into tomorrow's final in 24-carat condition.

The 25-year-old Welshman was not quite the fastest qualifier – the Puerto Rican Javier Culson clocking 48.52 seconds in his semi – but Greene was by far the most impressive, affording himself the luxury of taking his foot off the gas, Usain Bolt-style, with victory already in the bag.

"I've got to aim for the top of the podium," he said. "I'm going to give it everything. I know I'm running well. I'm firing on all cylinders. But there are a lot of guys running close at the moment, so it's going to be tough."

Culson, the 2009 World Championship silver medallist, and the American Bershawn Jackson – the 2005 world champion and winner of the third semi in 48.80sec – are the most likely threats to Greene. Defending champion Kerron Clement failed to qualify, a fate that also befell Greene's British team-mates Nathan Woodward and Jack Green, while Olympic champion Angelo Taylor only made the cut for the final as one of the fastest losers.

With a rest day from track and field action today, the women's 20km walk taking place on the roads, and four further sessions of finals to come in Daegu Stadium, the British team are three-sevenths of the way towards their pre-championship medal target – albeit with no gold on the board yet. Hopes of a podium challenge from Perri Shakes-Drayton came to grief yesterday when the young Londoner missed out on a place in the women's 400m hurdles final by 0.01sec.

At the age of 39, though, Yamile Aldama emerged as an outside contender in the triple jump, reaching the final with the fifth best qualifying mark of the day, 14.35 metres. A silver medallist for her native Cuba in 1999, the mother of two was making her debut appearance for Great Britain.

The destination of the men's 800m title has been in little doubt all summer, with David Rudisha maintaining the unbeaten form that took him to two world records last year. Still, the 2004 Olympic champion Yuriy Borzakovskiy of Russia stuck gamely to his heels before the Kenyan pulled clear in the home straight, winning in 1 minute 43.91sec.

There was an upset in the 400m, though, the 18-year-old Grenadian Kirani James pipping the wilting LaShawn Merritt to win in 44.60sec. "He didn't quite take it out hard enough," world-record holder Michael Johnson said of Merritt, who served a 21-month suspension after testing positive for an anabolic steroid contained in a male enhancement product.