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By Rod Gilmour
KAZAN, Russia, Aug 5 (Reuters) - Katie Ledecky's bid to become the first swimmer to win four individual freestyle titles at a world championships remained on track as the American claimed a stunning gold in the women's 200 metres on Wednesday.
After qualifying for the final in seventh during a punishing schedule which meant Ledecky raced her semi-final 30 minutes after winning the 1,500m freestyle gold with a world record, the 18-year-old American touched first in one minute 55.16 seconds.
Ledecky's win, achieved from lane seven, added to her golds in the 400m freestyle on the opening night and the 1,500.
With all eight swimmers in with a chance of a medal at the final turn, Federica Pellegrini of Italy denied a United States one-two by claiming silver in 1:55.32 seconds. World champion Missy Franklin took bronze in 1:55.49.
""It was a lot easier than the 1500m, it just didn't hurt as much and I knew I could put it all together," said Ledecky who hopes to add the 800m title on Saturday.
Sun Yang of China dug deep, also from lane seven, to win his second gold, the men's 800m freestyle, after a thrilling battle with Italy's Gregorio Paltrinieri.
European champion Paltrinieri looked in control of the race until Sun powered into the lead after 750 metres and touched the wall in 7:39.96. The Italian was 0.85 seconds down, in a European-record time. Mack Horton of Australia took bronze.
Briton Adam Peaty continued his fine form by adding the men's 50m breaststroke gold to his 100m breaststroke title, becoming the first swimmer to achieve the feat at a world championships.
Cameron van der Burgh of South Africa had to settle for silver once more as the Briton caught the world champion with the final stroke to win in 26.51 seconds.
Peaty won his third gold when he contributed to Britain's world-record time of 3:41.71 seconds in the mixed 4x100m medley relay, a new event.
"Every inch and every centimetre has been the hardest this week," said Peaty. "The 100m against Cameron was one of the hardest races of my life but I stepped up and didn't get taken away by the occasion tonight."
Defending champion Chad Le Clos of South Africa lost the men's 200m butterfly title to Hungarian Laszlo Cseh in an exciting final.
Le Clos led for the first 100 metres but the Hungarian regained the advantage by the final turn. Although Le Clos made one final surge, Cseh did enough to post the year's world-leading time of 1:53.48 and hold off the Olympic champion by 0.20 seconds.
Cseh's win vindicated his decision not to compete in the 200m individual medley.
"It was a hard decision," he told reporters. "I thought that I had to choose to swim really well in the butterfly final or swim okay in the medley."
Cameron McEvoy of Australia clocked the fastest time in the world this year, 47.94 seconds, as he topped qualification for Thursday's men's 100m freestyle final.
His bid to succeed compatriot James Magnussen, the double champion who was forced to pull out of the championships with a shoulder injury, was given a major boost when Russia's Vladimir Morozov was disqualified in the following heat.
Morozov led throughout to record 48.12 seconds but was adjudged to have left the blocks too soon, a decision which silenced the near-capacity Kazan Arena. (Editing by Clare Fallon)