Usain Bolt of Jamaica runs on his way to winning his 100m heat round 1 during the London 2012 Olympic Games at the Olympic Stadium August 4, 2012. [Photo/Agencies]

LONDON - Usain Bolt answers the nagging question of whether he is still the fastest man on Earth on Sunday in an Olympic cauldron that almost boiled over when Britain's athletes enjoyed their greatest night on Saturday.

The Jamaican won a golden treble with three astonishing world records at the last Olympics in Beijing. But since then he has lost his world title and his aura of invincibility.

Fans hoping the men's 100 metres final (2055 GMT) on the fast London track will top Beijing's may not have been reassured by the sight of Bolt stumbling in his heat but he was only in first gear and should glide through Sunday's semi-final.

The semis and the final later are also expected to include the three fastest men in history after Bolt - Jamaica's world champion Yohan Blake, compatriot Asafa Powell and Tyson Gay of the United States.

Asked by reporters on Saturday if he was in good enough shape to win gold, Bolt looked down at his feet and replied: "We'll see."

He can at least take inspiration from a crowd who cheered his first appearance to the hilt and from compatriot Shelly-Ann Fraser-Pryce, who on Saturday became only the third woman to win back-to-back Olympic 100 titles.

Women will also make sporting history in the boxing ring on Sunday when they compete on an Olympic stage for the first time, ending the last all-male sport at the Summer Games.

But if Sunday rewrites the record books, Saturday belonged to hosts Britain, who took three athletics golds and three more elsewhere to register their best day at an Olympics since the first London Games in 1908.