At the end of a gruelling race through Hyde Park — a 1,500-metre swim, a 43-kilometre bike ride and a 10-kilometre run — Switzerland's Spirig won gold in a photo finish.
Incredibly, both athletes recorded the same time: one hour 59 minutes 48 seconds.
In the end, Spirig held off a late charge by a surging Norden through the final few meters in one of the best triathlon finishes ever. The Swiss just thrust out her hips and upper body to win as the pair broke the tape together.
"Crossing the finish line I had a feeling that I had won but I wasn't sure," Spirig said. "I needed an official to tell me and it took a few minutes."
Both athletes celebrated. But only after they'd fallen to the ground, totally exhausted, alongside bronze medal winner Erin Densham of Australia following the sprint to the line.
After the initial uncertainty — and a few minutes of high drama — Spirig was declared the winner by the tiniest of margins on the photo finish. It was Switzerland's first medal at the London Games.
"We tried to put on a good show for you guys," Sweden's Norden said to reporters. "Nicola is an incredible sprinter, I've never been that close to her. I was surprised to find some energy still in my body and I pushed it all the way. I was close, but not quite."
Spirig initially pulled away from the other two with around 50 metres to go to the line.
But suddenly Norden — the tall blonde-haired Swede — found an extra bit of fight. Grimacing with the effort, she chased down her opponent over the final few steps of a near 55-kilometre battle and only just missed stealing the Olympic title.
In swimming, competitors share a medal if they have the same time. Not in triathlon, where — like track — the photo finish decides the winner.
"I think that would have been a great idea," silver medallist Norden said on being asked if they should have shared gold.
"I think that (the rule) was decided before the race," new Olympic champion Spirig said, smiling.
It was a tough day for Canada.
Paula Findlay of Edmonton finished last in 52nd, more than 12 minutes behind Spirig. While she has struggled with hip injury over the last year, Findlay said it was ''100 per cent'' Saturday
"It feels really good," she said. "I wish I would have had more time to prepare."
Findlay, who said her legs just weren't working, apologized as choked back tears at the finish line.
"I feel terrible," she said after the race. "I'm really sorry to everybody to Canada."
Findlay's teammate Kathy Tremblay of Pincourt, Que., also had a day to forget after she crashed during the bike race and did not finish.
The drama played out on a course through central London's famed park, where thousands of roaring spectators lined the route to egg on the athletes. Fans didn't need tickets to attend, and came out in droves.
They were rewarded with a thrilling end, even though reigning world champion and home favourite Helen Jenkins of Britain faded and finished fifth.
"It was a great race. A hard and strong race as well," Australia's Densham said. "The crowd was just incredible. It was deafening ... but really good and they surged us on."
Spirig said her ears were "ringing" from the crowd noise.
"It was like after listening to really loud music," she said.
Behind Densham, Sarah Groff of the United States was fourth in two hours flat ahead of Jenkins. Top-ranked triathlete Andrea Hewitt of New Zealand finished sixth.
Spirig always was in contention after the swim, where she emerged 18th. She soon found her way to the front during the bike ride, and stayed with the leading pack through the run.
It rained overnight, and some of the competitors crashed their bikes on the greasy track that wound through the park and past Buckingham Palace.
Norden was second to Germany's Anja Dittmer at the final transition from bike to run. But Spirig was hovering close behind in fourth.
Through the final part of the run, Spirig, Norden, Densham, Jenkins, Groff and Hewitt formed a breakaway group and the winner was certain to be one of the six.
Spirig pushed ahead in the last 200 metres, distancing Jenkins, Groff and Hewitt. But her Australian and Swedish challengers stubbornly stayed with her.
The No. 4-ranked Swiss kicked again about 50 metres out, leaving Densham behind this time and seemingly Norden as well. But the Swede never gave up, roared back and forced the desperate Spirig to fight all the way to the line for the biggest moment of her career.
"As an athlete, this is the highest I can reach," Spirig said.