LONDON, England (AP) — Dana Vollmer won a gold medal at the Olympics and set a world record, too.

Not bad for someone who didn’t even qualify four years ago.

On a night featuring a relay duel between the Australians and the Americans, Vollmer got things started with a bang yesterday in the 100-metre butterfly. She was third at the turn but powered to the wall for a time of 55.98 seconds, beating the record of 56.06 set by Sweden’s Sarah Sjostrom in a since-banned high-tech bodysuit at the 2009 world championships.

The American dropped back her head when she saw the time, then broke into a huge smile, slapped the water and pumped her fists.

“I’m on top of the world right now.” she said. “I still know I can go faster.”

Vollmer, who made the Olympics as a 16-year-old in 2004, was a huge disappointment when she failed to make the team in Beijing in 2008. She was slowed by injuries and health problems, making her question whether she even wanted to continue swimming.

But her injuries healed and a change in diet gave her a new outlook. She came close to breaking Sjostrom’s record at the US Olympic trials last month, and set an Olympic record in the semi-finals to come in as the top qualifier.

Now she’s an Olympic champion.

“I kept telling myself that my strength is my second 50,” Vollmer said. “I kept really calm.”

Lu Ying gave China another medal at the Olympic Aquatics Centre, taking silver in 56.87. Australia’s Alicia Coutts grabbed the bronze in 56.94.

“It’s not bad,” Lu said. “It’s the result, more or less, I hoped for.”

It was a tough night for Sjostrom. Not only did she lose her world record, she didn’t even get a medal, touching fourth in 57.17.

Vollmer was the second swimmer to set a world record at the London Games, and only the fourth to break a mark set during the rubberised suit era. Those suits were banned after an astonishing 43 world records were set at the 2009 World Championships.

The big race on the second night of swimming was the men’s 400 freestyle relay, which figured to be a duel between defending world champion Australia and the United States, which won the Olympic title four years ago.

The Americans sent out their big guns, going with Michael Phelps and Ryan Lochte in hopes of knocking off a favoured Aussies team that included James ‘The Missile’ Magnussen and James ‘The Rocket’ Roberts. Nathan Adrian and Cullen Jones also were swimming for the US, which changed up their entire line-up after qualifying second in the morning preliminaries.

The Aussies posted the fastest qualifying time with a quartet that included Magnussen and Roberts. They changed up the other two spots, going with Matt Targett and Eamon Sullivan.

There were two other finals Sunday night.

In the men’s 100 breaststroke, Japan’s Kosuke Kitajima was attempting to become the first male swimmer to win the same individual event at three straight Olympics. Phelps failed miserably at his attempt the night before, failing to even medal in the 400 individual medley. Also, Britain’s Rebecca Adlington looked to give the home country its first swimming medal and defend her title in the 400 freestyle.