LONDON  - World record holder Usain Bolt and world champion Yohan Blake stormed onto centre-stage at the Olympics on Saturday as amputee runner Oscar Pistorius made history. Defending 100m champion Bolt clocked 10.09sec in his first round heat for the blue riband event of the Games while Jamaican compatriot Blake timed 10sec.

However, both men were upstaged in front of 80,000 people at the Olympic Stadium by the 9.88sec run by America's Ryan Bailey. Former Olympic champion Justin Gatlin clocked 9.97sec while Tyson Gay, the world double sprint champion from Osaka in 2007, came through in 10.08sec.

"I expected it, I'm running well, I'm happy, training is great. Reaction was good," said Bolt, whose build-up to the Games had been hit by a number of worrying niggles. "I'm looking forward to the semi-finals." South Africa's Pistorius marked his landmark occasion by qualifying for the 400m semi-finals with a season's best of 45.44sec. Pistorius had both legs amputated below the knee before he was aged one, because of a congenital condition, and runs on carbon fibre blades. "It's just an experience to be here. It's a dream come true," said Pistorius, whose time was the 16th fastest overall. Defending champion LaShawn Merritt, who has struggled back from a doping ban, stopped running after 250 metres of his heat and crossed the line at walking pace.

The women's 100m gold will be decided in Saturday's evening session while Jessica Ennis, the poster girl for the Games, was poised for heptathlon gold, opening a 188-point lead with just the 800m to run. Women's double Olympic polevault champion Yelena Isinbayeva safely negotiated qualifying for Monday's final.

On the busiest day of the Games so far, with 25 golds to be won, Britain moved into third place in the medals table after two more golds were secured in rowing and one in women team pursuit cycling event. Alex Gregory, Pete Reed, Tom James and Andrew Triggs Hodge led from the first stroke for a fourth successive fours title while Katherine Copeland and Sophie Hosking clinched lightweight double sculls gold. Hosts Britain collected their fourth gold medal from five events at the Olympic velodrome after the women's pursuit team triumphed in a new world record time of 3min 14.051sec. The USA finished second to take the silver with Canada completing the podium in the inaugural Olympic women's event, held over 3 km and 12 laps as opposed to 4 km and 16 for the men.

Chen Ding won China's first ever men's Olympic 20 kilometres walk title and first ever medal in the event coming home in a time of 1hr 18 min 46sec. The 19-year-old beat home Guatemalan Erick Barrondo, who gave his country their first ever Olympic medal in any sport, while another Chinese walker, Wang Zhen, was third. Defending champion Valeriy Borchin of Russia collapsed and lay distressed against a barrier within two kilometres of the finish while he was in fourth place and had to be stretchered away by medical staff.

Ranomi Kromowidjojo of the Netherlands won the Olympic swimming 50m freestyle gold medal in a time of 24.05sec. Aliaksandra Herasimenia of Belarus earned silver in 24.28 and Marleen Veldhuis of the Netherlands took bronze as Beijing gold medallist Britta Steffen was relegated to fourth. Among the other medals decided on a hectic day was a thrilling women's triathlon that went down to a photo-finish, the first ever in the sport. After just shy of two hours of racing, Swiss Nicola Spirig was judged to have beaten Lisa Norden of Sweden by 15 centimeters after a ferocious sprint finish in Hyde Park in central London.

Away from the sporting action, Colombian 400 runner Diego Palomeque Echevarria was temporarily banned from the Games following a positive test for testosterone, the International Olympic Committee said.