Chinese teenager Ye Shiwen stunned the world again as she calmly took her second Olympic gold medal in the women's 200m individual medley in London's Aquatic Centre on Tuesday night.

The 16-year-old finished in 2:07.57, earning her a new Olympic record.

When the eight swimmers took to the blocks before the start, it was hard to guess, from their demeanor at least, which of them would end up standing atop the podium.

All the swimmers had the same pre-swim routine - waving to the crowd, adjusting their caps, goggles and swimwear and warming up.

British Hannah Miley, in lane one, this event's record holder, was greeted with an enormous roar by the home fans. But it was Ye, the girl with the white cap in lane four, who drew most of the attention.

The thrilling final 50m saw Ye take the lead from Australia's Alicia Coutts, and made her a double Olympic champion in a single Games.

Coutts took silver in 2:08.15 and American Caitlin Leverenz claimed the bronze in 2:08.95. Miley finished in seventh place.

Over the past two days, the world of swimming has been embroiled in controversy over how the teenager could achieve such an astonishing performance, but Ye has remained silent and focused on her swimming, leaving both the allegations and her opponents behind.

Ye's victory was not a foregone conclusion. The teenager was not the leader out the blocks, she turned only in fourth place after the first 50m butterfly. She pulled back some ground in the middle 100m to turn in second, but it was on the final freestyle leg that she powered away.

On Saturday, Ye surprised watchers in the women's 400m medley, swimming a final freestyle leg and showing an extreme acceleration, finishing almost three meters ahead in a time which broke the previous world record.

"I promise that I have not taken any of the banned drugs," said Ye during the post-match press conference when media asked about whether doping claims.

"Indeed, they may be biased toward me. If the gold medal went to other countries, there would not be such huge suspicions, but it went to a Chinese so they are full of questions," Ye said. "It is not fair, but it will not affect me; I will just take it easy."