Four years after he bore the disappointment of a nation when injury denied him the chance to defend his 110 metres hurdles title on home soil in Beijing, Olympic heartbreak struck again for Liu Xiang.

The 2004 champion, one of the favourites for the gold medal in London, suffered a recurrence of an Achilles injury and was unable to make it over the first barrier in his heat this morning.

The 29-year-old clattered the hurdle and fell before limping determinedly down the track toward the finish line, Great Britain's Andy Turner, the heat winner, one of those to help him away.

The disappointment echoed that of four years ago when Liu stunned the crowd by walking off the start line, unable to run because of an Achilles problem.

"I feel really sorry about this situation," said Feng Shuyong, the head coach of the Chinese athletics team.

"We think it was like four years ago, the same thing happened again.

"I feel really sad because he has worked very hard to get back to the level he was at before as champion.

"What I saw on the big screen was that he could not take off. I think the problem just happened with that.

At the moment of take off the tendon would bear very, very big pressure. He could not make the movement.

"You see him running well in certain competitions, but not many people know how he achieves this level. That's why I appreciate a lot his hard work and his very strong willpower.

"Seeing him hopping to the line shows the true spirit of the Olympics, he was still determined to go to the line."

It was a sad end for an athlete acknowledged as one of the world's greatest ever hurdlers.

Aries Merritt, world number one, said: "It's just a tragedy for that to happen to one of the best hurdlers of all time.

"I hope he's okay. It's a shame that had to happen to Liu.

"He looked fine before the race. He was happy. I don't think anything was wrong, I think he just made a small mistake and when you do that at this speed it's hard to recover."

Turner said: "I regard him as probably the best hurdler in history and have so much respect for him. It was horrible seeing him limp off like that so you have to go and help people."

The pair both made the podium at last year's World Championships in Daegu when Turner took the bronze and Liu the silver.

The Briton added: "When you medal with people you have a kind of connection and after last year in Daegu we always say hello and try and have a chat in what little English he speaks. He's a nice guy and I wouldn't wish that on my worst enemy."