The American quarter finished in 3:32.31, just 12 hundredths of a second ahead of the Australians to give Franklin, who was one of the sensations of the 2012 Olympics, her first gold medal of the Championships, although it was Megan Romano who spoke for the team.

"The Australians started strongly, but all of our team was strong and that made it easy for me on the anchor leg," she commented, modestly highlighting the fact that the entire team had swum fast times, without mentioning her anchor leg of 52.60 had taken them to a new American record.

However, American hopes of a gold winning treble in the first day in the pool came to a spectacular end when the French came from behind to take gold in the 4x100 men's freestyle relay.

China's Sun Yang reacts after winning the men's 400m freestyle final during the World Swimming Championships at the Sant Jordi arena in Barcelona July 28, 2013.   [Photo/Agencies]

The Americans had looked to be on their way to gold as Nathan Adrian and Ryan Lochte swam solid opening legs to give them a half second lead in the race before Fabien Gilot got the French into contention with a third leg of 46.90 seconds.

Jeremy Stravius then swam a magnificent anchor leg to come from behind and give the French gold in a race which had looked to belong to the American's after the first two legs.

"Everything happened very fast as we came back, but we are all very happy," said Gilot.

"The French relay team now has something beautiful to live again. It was a big challenge to succeed in this race, but our strategy paid off and we succeeded," he said, delighted at the support the team had received from the numerous French supporters in the Barcelona pool

"I felt like we were at home," he said, while the American's were clearly shocked to have failed to win the World Championship gold for the first time in 10 years and admitted they had not expected the French to challenge.

The Russian quartet also produced an exceptional swim which saw them finish just 0.2 second behind the Americans to take the bronze medal ahead of the Australian team, which disappointed as it had done in London 12 months earlier.