Gwangju     -   Katie Ledecky is usually there in the end, her endurance powering her to the wall well ahead of the competition.

Someone else got there first at the world championships on Sunday night. Ariarne Titmus of Australia chased down Ledecky over the last lap to win the 400-meter freestyle and deny the American star a record fourth straight title. It was Ledecky’s first defeat in the event at a major international meet since 2013. “This stings a little,” Ledecky said. “It’s not what I’m used to.”

China’s Sun Yang was able to do what Ledecky could not: win his record fourth consecutive title in the men’s 400 free. As expected, it didn’t come without controversy. Sun’s rival, Mack Horton of Australia, ignored Sun on the medals podium. They didn’t shake hands and Horton didn’t even step onto the podium; instead he stood behind it when given his silver medal.

Titmus overcame a 0.62-second deficit going into the last lap and won by 1.21 seconds over Ledecky. The 18-year-old Aussie touched in 3 minutes, 58.76 seconds. Ledecky finished in 3:59.97 — well off her world record of 3:56.46 set at the 2016 Rio de Janeiro Olympics.

American Leah Smith took bronze in 4:01.29. An admittedly nervous Ledecky had the slowest last lap of anyone in the eight-woman final. Titmus went 1.83 seconds faster over the last 50 meters. Titmus led through the first 200 meters — dipping under world-record pace on the first lap — before Ledecky moved in front with 250 meters to go. The American was still ahead turning for home. But Titmus pulled even midway through the last lap and surged to the wall first, becoming the first Aussie to win since Tracey Wickham in 1978.

In the men’s 400 free, Sun worked his way from fifth to first and then easily kept Horton at bay over the last lap to surpass Aussie great Ian Thorpe’s record of three straight wins. He touched first in 3:42.44. Horton took silver in 2:43.17, while Gabriele Detti of Italy earned bronze in 3:43.23. Sun climbed on the lane rope and waved four fingers on each hand in celebration. He pounded the water and was the last swimmer to leave the pool.  Sun won his other 400 free titles in 2013, 2015 and 2017. His presence at the world meet has drawn the ire of some swimmers, including Horton and American Lilly King. The Aussie is the only swimmer to beat Sun in the last eight years, taking gold in the 400 free at the Rio Olympics in 2016.

That’s when Horton called Sun a “drug cheat” for his three-month doping suspension in 2014.

In the men’s 4x100 freestyle relay, Nathan Adrian anchored the Americans to a victory seven months after announcing he had been diagnosed with testicular cancer. Their time of 3:09.06 was a championship record, lowering the mark of 3:09.21 set by the U.S. in 2009 during the high-tech suit era. The women’s 4x100 free relay went to Australia in 3:30.21, also a championship record. The U.S. took silver and Canada earned bronze.

Adam Peaty of Britain became the first man to go under 57 seconds in the 100 breaststroke. He won his semifinal heat in 56.88 seconds, bettering his old world record of 57.10 set last August in Glasgow, Scotland. Peaty is seeking his third straight world title in the event. He also won the 100 breast at the Rio Olympics.