Thorpe fought back tears as he paid tribute to his Australian teammate Craig Stevens who volunteered to step down from the race for him.

"I had a wonderful opportunity to swim this race because one of my best friends chose to give me this opportunity and I'm very grateful for that," Thorpe said.

"I treasure this experience more than winning the actual medal itself."

Thorpe, 21, has not lost a 400 freestyle race in seven years but his chances of becoming just the second man in history to win the event at two Olympics appeared sunk when he slipped off the blocks and was disqualified for a false start at this year's Australian trials.

He lost an appeal against his disqualification but was thrown a lifeline when Stevens, who had finished second behind Grant Hackett at the trials, pulled out to concentrate on his other events.

Thorpe, whose new coach Tracey Menzies was also drawn into the saga after being blamed for the clumsy false start, said it was a relief for everyone that he was able to win in Athens.

"This has been a very emotional six months," said Thorpe, who now has four Olympic gold medals.

"I was probably swimming the race for other people besides myself and that's the first time I've done that.

"It was worth it and I wouldn't change anything but it probably wasn't the most efficient way of swimming it my best."

Thorpe hit the front halfway through the final but had to survive a late charge from Hackett before claiming the gold in three minutes 43.10 seconds, more than three seconds outside his world record.

"I didn't swim the race well, there's no two ways about it. I just missed it, I wasn't on my game tonight," he said.

"It was a different experience here to what it was in Sydney. It was tough out there and I am relieved the race is over.

"I said that it was more difficult to defend than what it is to gain an Olympic title and it's only true because of everything else that goes on around it, to stay focused and committed to what you're doing."