Thorpe, having his first competitive race since Athens Olympics,finished his heat first in 47.87 seconds, 0.16 faster than his nearest rival, South African Ryk Neethling, on Saturday morning.

However, the five-time Olympic gold medalist, who has just recovered from a 15-month break because of bronchitis, announced his withdrawal, saying that he was happy with his morning swim but had not been feeling well

"Ian has not been well this week and missed a couple of training sessions and he felt it was better that he did not swim tonight,"national head coach Alan Thompson said in a statement, expressing his satisfaction with Thorpe's comeback performance.

Thorpe's next race will be at the New South Wales state championships in December while next major meet will be the Commonwealth Games in Melbourne in March. Enditem