By Julian Linden

LONDON, July 29 (Reuters) – Dana Vollmer ended a lifetime of frustration and battles with her health to win the 100 meters butterfly gold medal in world record time at the London Olympics on Sunday.

The American, swimming like a woman possessed, powered her way through two laps of the Aquatic Centre to win in 55.98 seconds, slicing 0.08 off the previous mark set by Sweden’s Sarah Sjostrom at the 2009 world championships in Rome.

China’s Lu Ying finished second while Australia’s Alicia Coutts, a gold medallist in the 4×100 freestyle relay on Saturday, was third and Sjostrom fourth but all the plaudits went to Vollmer.

While Vollmer won a relay gold medal at the 2004 Olympics in Athens, the 24-year-old had never competed in an individual event at the Games before London.

In 2000, she was a bright-eyed 12-year-old at the U.S. trials and did not qualify for the Games at all. In 2004 she was a surprise qualifier, but only in relay, and was earmarked as a future champion.

In 2008, however, the combination of a mystery illness and the weight of expectation got the better of her and she failed to make the American team.

In 2003, she underwent heart surgery to correct a condition which produced a faster than normal pulse and forced her to take a defibrillator to all her races and training sessions.

But it was an allergy to eggs that held her back for many more years. When it was finally diagnosed, after missing out on the Beijing Olympic team, she was put on a new gluten-free diet.

Her results in the pool quickly started to improve and in 2011 she won her first individual world title at Shanghai.

She had come close to breaking the record before only to run out of puff in the final few meters but swam a more even race this time, reaching the halfway point in third place then surging away on the last lap.