Pellegrini wins 400 free

The 22-year-old Italian had sat behind the leaders for the first half of the race and turned at the 200m mark in fifth place, before she took control on the fifth lap and turned with 150 metres to go in firm control.

"I'm very happy to confirm myself as a world champion again," Pellegrini said. "It's always very difficult to win.

"After the competition, I shaped a heart to my athletic trainer out of gratitude."

Beijing Olympic champion Rebecca Adlington, who had qualified in seventh and was forced to swim in lane one, never lost touch with the leaders and swum over the top of France's Camille Muffat to take silver in 4:04.01. Muffat was a fingernail behind in 4:04.06 for bronze.

"I'm so pleased with that swim after this morning," said Adlington. "I was quite down after my heat as I didn't expect to swim so slowly but I picked myself up and that was so much more positive tonight.

 "I tried to stay with Kylie Palmer and from my outside lane didn't really see anyone else.

 "I saw a pair of feet in the distance, figured it was Pellegrini and knew I couldn't catch her as she's so far ahead at the moment.

 "Pellegrini is an amazing athlete and I'm just please to get the silver behind her. Two years ago in Rome I took the bronze so this meet is better for me already."

New Zealand's Lauren Boyle, who had qualified third fastest after winning the fifth heat in the morning session in a national record and had hoped to become her country's first world championships medallist since Trent Bray won bronze in the 200 freestyle in Perth in 1998, finishing sixth.