The 17-year-old from California (pictured top, in centre), who is tipped to be one of the stars of these Olympics, lined up for the final less than half-an-hour after she qualified for the final of the 200m freestyle.

But looking completely unflustered Franklin claimed the win in 58.33sec with Australia's Emily Seebohm, the pre-race favourite, taking silver in 58.68 and Japan's Aya Terakawa bronze in 58.83.

The win marks Franklin's first gold and second medal in her Olympic debut after she swam in the American 4x100m freestyle relay team that claimed silver behind Australia earlier this week.

"I am so happy," said an elated Franklin after the race.

"I knew it was going to be difficult but I had a blast out there tonight.

"I got so much advice from the team with all my events but the best advice from my coach has been to take it one event at a time and to relax."

US star Ryan Lochte is dismayed after finishing without a medal in the men's 200m freestyle

Franklin's win contrasted with a strangely below par performance from compatriot Ryan Lochte, who could not add to the gold and silver medals he has already won at these Olympics after finishing fourth in the men's 200m freestyle and well down on the winner, Yannick Agnel of France.

"I can go a lot faster," said a disgruntled Lochte, who still remains on track for more medals at London 2012.

"I don't really know where I fell off."

His disappointment was mirrored by the British team after Liam Tancock finished fifth in the 100m backstroke final, an event won in an Olympic record time of 52.16 by American Matt Grevers.

Gemma Spofforth finished fifth in the women's equivalent race and Robbie Renwick came a distant sixth in the 200m freestyle.

Tancock, who has won a medal at every major senior international event bar the Olympics, looked to focus on the positives.

"I went out there and gave it everything but it didn't quite come off for me," he said.

Briton Gemma Spofforth finished in fifth place in the women's 100m backstroke 

"But Rio is only four years away and I just love what I do.

"Swimming is an amazing sport and it's an absolute dream to swim in a pool like this, in front of a crowd like this."

Elsewhere, American star Michael Phelps qualified easily for the men's 200m butterfly final tomorrow.

Should he win the event he will become the first male swimmer to claim gold in the same individual event at three successive Olympics.

He will also equal Soviet gymnast Larisa Latynina's long-held record tally of 18 Olympic medals.

Phelps could then claim the outright record when he contests the 4x200m freestyle relay event later this week when the Americans are overwhelming favourites to win.

Contact the writer of this story at [email protected]


Related stories
July 2012: Agnel inspires France 4x100m freestyle team to thrilling swimming success over US
July 2012: Swim queen Adlington exceeds expectation by claiming 400m freestyle bronze
July 2012: Duel in the pool goes Lochte's way as Ye smashes world record