Austria's Kate Allen won the Olympic women's triathlon title with a stunning final leg on the run.
Allen started the 10km run almost three minutes off the pace and Australia's Loretta Harrop looked set for gold.
But as Harrop came into the home straight Allen breezed past for a memorable and unexpected win.
Allen finished in two hours 4.43 minutes, seven seconds ahead of Harrop with America's Susan Williams in third and Britain's Michelle Dillon sixth.
"It's unbelievable and a great surprise," said Allen, who conceded she had set out to realistically finish with a good place outside the medals.
"I'm in the shape of my life, running is my strongest discipline and when I saw Loretta I had that little bit extra and I went for it."
It was a cruel conclusion for Harrop who had led from the front almost throughout.
She came out of the Aegean Sea after the 1500m swim just behind the American Sheila Taormina and the pair then proceeded to work well together on the 40km bike ride.
The challenging five-lap eight-kilometre course, including an 18-degree 700-metre hill, saw them establish a huge advantage - on just the first lap.
That 40-second lead was soon up to almost a minute, and when Harrop broke Taormina on the fifth and final ride up the tortuous climb and set off on the run with a 20-second lead, it seemed the only race would be left for the minor medals.
But Allen had other ideas.
Having come out of the water in 44th place, she worked her way up to 28th on the bike before setting about hunting down Harrop, despite starting the run almost three minutes in arrears.
The Australian-born athlete picked off her peers moving through the field with ease before bearing down on victory in the closing stages.
Allen burst past Harrop as she turned into the home straight and broke the line seven seconds ahead of the beleaguered long-time leader.
Dillon was unhappy with swim tactics
Like Allen, Britain's Michelle Dillon also made up ground with the third fastest run of the day to finish sixth. Compatriots Julie Dibens and Jodie Swallow finished 30th and 34th respectively.
But while Dillon was pleased with her run, she accused fellow-competitors of dirty tricks in the sea.
"People were pulling my zipper down in the swim," she revealed.
"They were obviously trying to pull me back, which is really disappointing.
"I couldn't believe people were doing that. Luckily the zipper didn't come down and once I got on to the bike I was OK."
Swallow insisted she had made the right decision in coming to Athens, depsite an "awful" triathlon.
The star was controversially picked for the squad, even though fitness problems meant she hadn't competed since the start of the year.
Swallow, who trailed home in 34th place, insisted: "I got the best qualifying criteria.
"It was pretty awful and I feel absolutely awful, but all credit to myself - I toughed it out."