Swiss Nicola Spirig won the gold medal in the London 2012 women's triathlon in the sport's first photo-finish at the Olympics on Saturday.
After a ferocious sprint finish in Hyde Park, both Spirig and Lisa Norden of Sweden were given the same time of one hour 59 minutes 48 seconds.
The judges examined the photographic evidence and said Spirig's winning margin was less than 15 centimetres.
Two seconds back, Erin Densham of Australia won the bronze medal, having been in contention for gold until the final 200 metres.
"I had a feeling but I wasn't really sure," the 30-year-old Spirig said when asked if she knew she had won the gold medal. "I really needed an official to tell me. It took a few minutes and those minutes were really hard."
Fourth was Sarah Groff of the United States, in two hours dead, while British world champion Helen Jenkins was fifth, 19 seconds further back.
The swimming, cycling and running course took in some of the British capital's most famous landmarks, including Buckingham Palace.
It began with a 1.5-km swim in the Serpentine lake in Hyde Park on a day cold enough, with a water temperature of less than 20 degrees Celsius, to allow the women to wear wetsuits.
The wetsuits assisted the weaker swimmers and led to almost half the field of 56 starters, including the pre-race favourites, forming a lead group on the 43-km cycle phase.
London's roads, wet from overnight rain, claimed some early casualties including Australia's Emma Moffatt, the 2008 Olympic bronze medal-winner, who was involved in a five-woman crash on the first lap.
Vicky Holland, in the British team as a domestique to help Jenkins's cause, was brought down in the incident, leaving her unable to assist the favourite.
"I was here to do everything I could to help Helen and I wasn't able to help her," Holland said. "It was like a waiting game, which is not what we wanted."
On the 10-km run, over four laps around the park, strong pace-setting by Densham and Jenkins whittled down the challengers until, into the final lap, five remained in contention.
Jenkins was the first to crack, to the shock of the huge crowd. Going into the final straight beside the lake, Spirig, sixth in Beijing four years ago, launched a surge for home.
Only Norden could keep with her, throwing herself across the line in a late but ultimately unsuccessful lunge for gold.