The lead-up to this summer’s World Championships has been dominated by doping revelations, but starting on Saturday the athletes have a chance to lift their sport from the mire.
Here, Sportsmail looks at the key battles and debates, and pinpoints Britain’s best medal hopes…
100 metres heats, Saturday, 12.20pm
The best fairytales are usually a battle between good and evil, and sprint hero Usain Bolt against athletics’ highest-profile villain, double drugs cheat Justin Gatlin, promises to be the highlight of these Championships.
Bolt will need to produce something special to beat the American, who is unbeaten in 27 races and has run 9.74sec this season.
Bolt’s season’s best is 9.78sec at the Anniversary Games and he will probably have to go under 9.7sec to get the better of Gatlin, something he last did when winning gold at the London Olympics in 9.63sec. Two days later they do it all again in the 200m. DAVID RUDISHA vs NIJEL AMOS
800 metres final, Tuesday, 12.55pm
Kenyan Rudisha front-running like a gazelle on his way to victory and a world record of 1min 40.91sec in the 800m was a defining moment of London 2012, his pace so punishing that Amos had to be taken from the track on a stretcher.
How the tables have turned. Rudisha was beaten by Botswana’s Amos at the Commonwealth Games in Glasgow last year and was outsprinted by him again in a Diamond League meeting in Switzerland and at the Anniversary Games last month.
Amos is the favourite to notch another victory in China.
4 x 100 metres relay, August 29, 1.50pm
Jamaica’s defeat by America when their almost full-strength teams met at the World Relay Championships in the Bahamas in April was Bolt’s first loss since 2007 and he will be hungry to avenge it here, probably running the anchor leg against Gatlin.
America’s line-up is likely to include three drugs cheats in Gatlin, Tyson Gay and Mike Rodgers. A victory for Jamaica is hardly a win for clean sport, though, with Asafa Powell — who tested positive for the amphetamine oxilofrene — captaining his country.

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