The race to be crowned world’s fastest man takes centre stage at the Olympics today as Usain Bolt bids to defend his 100m title in what is being billed as potentially the quickest race in history.

After an electrifying “Super Saturday,” Bolt and his rivals for the blue riband event of track and field are poised to serve up more pyrotechnics as 80,000 fans pack the Olympic Stadium.

Barring major surprises, the starting line-up for the late night showpiece could feature five men who have clocked a blistering 9.8sec or faster, including world record holder Bolt.

The Jamaican defending champion strolled through his opening heat on Saturday, but faces a menacing threat to his supremacy from compatriot and world champion Yohan Blake.

With former world record holder Asafa Powell and American duo Tyson Gay and Justin Gatlin in the field, the stage is set for a classic sprint duel.

Sunday’s athletics programme kicked off with the women’s marathon, starting and finishing in the Mall in central London, near Buckingham Palace, and taking in many of the city’s most famous landmarks.

A total of 23 medals will be decided on Day 9 of the Games, where other highlights include the men’s singles tennis final at Wimbledon between world number one Roger Federer and British hope Andy Murray.

The final two medals in one of the Olympics other racquet sports, badminton, will be decided when China’s world number one Lin Dan faces Malaysian rival Lee Chong Wei in the latest instalment of their long rivalry.

In men’s and women’s artistic gymnastics, the apparatus finals for men’s floor and pommel horse take place either side of the women’s vault.

Elsewhere, women’s boxing will make its debut in Olympic competition with the opening bouts in the women’s flyweight and lightweight categories.

Meanwhile, Sunday was also the first day of Michael Phelps’s new life after the most successful Olympian of all time quit swimming.

“Through the ups and downs, I have achieved everything I ever wanted to do,” said Phelps who ended his career with 22 Olympic medals, 18 of them gold.