The 29-year-old former world record holder — winner of the 2004 Olympic crown —had been left distraught four years ago after he was forced to withdraw just moments before his opening race in front of his home fans. But his return to the Olympic arena lasted only a split second when he ploughed into the first hurdle with his left leading leg and crashed heavily to the floor.

Liu, who has been troubled by back and foot problems in the past month, eventually got up and hopped down the track to be embraced by his fellow competitors. He was helped off the track by Britain’s Andy Turner and Spain’s Jackson Quinonez and then taken to the medical centre in a wheelchair.