Nicola Spirig sprinted to one of the most dramatic victories at the London Olympics four years ago and the triathlon gold medallist knows it will take an even greater effort to defend her title in Rio.

Spirig produced an incredible exhibition of endurance in Hyde Park, surging to the line alongside Lisa Norden in one last desperate attempt to take gold.

The indefatigable Swiss athlete and Norden had to endure a tense wait to discover who would top the podium, as a photo finish was needed to separate the two.

It was Spirig who was given the verdict and the 34-year-old looks back on her finest hour with great pride as she prepares for a final assault on the Olympics in Brazil.

She told Omnisport: "It's still very emotional when I think back to London. After the close finish I didn't know if I had won as it was so close between first and second.

"The minutes to the decision seemed to be years. I was relieved the race was over, very happy it had gone well, proud of myself to have given my best, thankful for all the support I had.

"But really it hadn't sunk in that I might be the Olympic champion back then.

"To hear the national anthem on the podium at an Olympic Games is extremely special and emotional.

"I thought of my grandfather sitting at home in front of a TV about 48 centimetres away from the screen, as he was nearly blind, and knew he would be extremely proud. I thought of everyone who had helped me to get there.

"I am one of only four women in history from Switzerland who won gold at summer Olympics, therefore it is something very special."

Spirig broke her hand in March after suffering a crash on the bike during the World Triathlon Series race in Abu Dhabi, but was back in training less than 48 hours after undergoing surgery.

The Bulach-born triathlete is in the twilight of her career and has a burning desire to have another Olympic medal around her neck in Rio, but is aware a monumental effort is needed to pull off a repeat of her success in England.

She added: "It is very difficult to win a gold medal, and even much more difficult to add another one, no one in triathlon has ever done that.

"It's a big puzzle and all the puzzle pieces need to be correct to win a gold medal, but I will prepare for Rio as best as I can.

"There are several very good athletes at the moment and it depends on the way the race is going who will be the biggest rivals."

Spirig has not decided what the future will hold after Rio, but with a law degree and a gold medal in the bank she will surely not be short of offers.

"I only planned until Rio, we will see what happens afterwards, a decision I will make together with my family." Spirig said.

The Olympic champion was considering an attempt to represent her country in the marathon in Rio, not content with just the small matter of a 1.5 kilometre swim, 40km cycle and 10km run.

Regardless of what happens next month, it will require something special to top the pulsating finale that resulted in Spirig being crowned champion in London.