* Olympic champion Park disqualified then reinstated
* FINA decision sets up Asian duel (Adds race result, quotes)
By Alan Baldwin
LONDON, July 28 Park Tae-hwan surrendered his Olympic 400 metres freestyle title after a roller-coaster first day in the Olympic pool that started with a shock disqualification and ended with reinstatement and a silver medal.
"Today has been a long day for me," he told reporters after ending up well beaten by Sun Yang, China's first male Olympic swimming gold medallist.
A national hero to his compatriots after he overcame childhood asthma to become the first South Korean swimmer to win Olympic gold in Beijing four years ago, Park appeared in the morning to have blown his chance.
After a protest, and several hours of deliberation, governing body FINA back-tracked on the referee's decision that it was a false start.
They decided he could compete in the evening's final at the expense of Canadian eighth-placed qualifier Ryan Cochrane, who missed out by one hundredth of a second.
Park, who had been told by his coach to rest and have lunch pending the appeal, made the fastest start of anyone in the final and set a world record pace for the first 300 metres before fading.
He did not dwell on the stress but indicated it had played a part in his defeat.
"Because of the decision, which was unfortunate, it was very difficult for me during this period after the heats and before the final," he said. "I'm sure there was some influence."
FINA said the unusual reversal was based on the recommendation of its technical swimming commission but provided no further details in a one paragraph statement that begged plenty of questions.
A venue press officer sitting alongside Park at a post-race news conference tried to intervene when questions were asked about the disqualification, telling reporters to email FINA instead of asking the athlete.
A FINA official earlier said the disqualification had been based on what the referee had seen.
Timing is done by Omega, who have introduced new electronic sensor pads on the blocks for London to measure swimmers' reaction times, but only the referee can declare the disqualification.
Reinstatements are rare but FINA has performed similar U-turns before. At the 2004 Athens Olympics, American Aaron Peirsol was reinstated as the winner of the 200m backstroke after winning an appeal against his disqualification.
Park seemed to have made a schoolboy error in moving too early for a heat he should have won easily, a mistake that provided a flashback to his Olympic debut in 2004 when he was also disqualified from his preliminary heat in the same distance.
The youngest South Korean athlete at those Athens Games, he was so upset he hid in a bathroom for hours.
On Saturday he also momentarily hunched up on the floor, wiping his eyes, but it was more out of relief and happiness than despair.
"The coach said to forget about today and tomorrow we focus on the heats," he said. "I need to throw this thing away so I can really focus. It's not going to be easy but I will try."
Park had been expected to take on the mantle of retired Australian Ian Thorpe as the dominant swimmer in the men's 400 after his Beijing win but has struggled to assert his authority on the distance.
After the last Olympics, he failed to qualify for the final at the 2009 world championships in Rome but won the title in Shanghai last July despite scraping into the last eight with only the seventh best time. (Additional reporting by Clara Ferreira-Marques, editing by Julian Linden)