Michael Phelps has eased his way into the final of the men's 200 metres butterfly to remain on course to cap his incredible Olympic career with more record milestones.
After crawling through the first two laps of his favourite event in the middle of the field, he turned on the power in the last two lengths to win his semi-final in one minute, 54.43 seconds.
That left him fourth fastest overall behind Japan's Takeshi Matsuda, who set the pace at 1:54.25.
The 200 butterfly is one of the most physically demanding events in swimming but is also Phelps' favourite.
He swam it at the Sydney Olympics when he was just a 15-year-old and has won the gold at the past two Olympics.
"When I came out of the first 100 I looked up at the scoreboard and saw the time, so very, very slow. I wanted to put myself in a good position for the final," he said.
"I was out pretty slow. I'll have to have a different strategy for tomorrow."
By his standards in Beijing, where he won eight gold medals, Phelps has had a slow start in London.
He finished fourth in the 400 individual medley then was part of the silver medal winning 4x100 freestyle relay team, but if he wins Tuesday's butterfly final, he will become the first male swimmer to win gold in the same individual event at three successive Olympics.
"I made my first Olympic team in this. The shorter races are a lot better for me now that I'm older," he said.
"I feel a lot better now. I'm a lot happier. I'm back on track."