Eaton led the 22-man field overnight after five events. He was 173 points ahead of Damian Warner from Canada. Rico Freimuth from Germany was third.
When hostilities resumed on Saturday morning, Warner cut into the advantage by 42 points after the sixth and seventh disciplines of the 110 metres hurdles and the discus.
But Eaton reasserted his authority by clearing 5.20m in the eighth event of the pole vault while Warner could only manage 4.80. Eaton was again better in the penultimate round of the javelin.
With 8,216 points from nine events, that meant Eaton’s world record of 8,039 was in sight. To achieve it he would need to run the 1500 metres in 4:18.25 to set the record. Eaton crossed the line in 4:17.82. It furnished him with 829 points and a new world high of 8,045.
Eaton, who won gold at the 2012 London Olympics, revealed he was inspired to attempt the world record by Freimuth, who also needed a fast time in the 1500 metres to ensure the bronze medal. Eaton said: “Rico’s like: ‘I’m going to do this. I’m going to go for it.’ And that’s when I said: ‘OK he’s going to go for it. He’s going to be tough. So I’m going to be like Rico and I’m going to go for it too.’”
Warner picked up the silver medal.
Eaton’s win is all the more remarkable since he withdrew from the decathlon for two years to concentrate on the 400m hurdles. He said he had developed new techniques for the hurdles during his sabbatical but conceded he missed the decathletes’ esprit de corps.
“I’m always trying to beat myself. That’s very difficult and you need support doing that,” he said. “I use the other decathlon competitors to push me to beat myself. I see their successes and I think: yes, I can do something too and I get fired up to compete and so that’s the camaraderie. It comes from each of us knowing that we are trying to beat ourselves but that we need each other to do that.”
Warner set a Canadian national record of 8,659 on his way to the gold medal at the Pan-American Games in Toronto last month.
He said the victory in front of his home crowds had given him a boost for the Beijing championships. He was within touching distance of Eaton until losing too much ground after the eighth event of the pole vault.
Eaton cleared 5.20m to gain 972 points while Warner’s 4.60 only brought him 849 points. The margin of 254 points was too much to make up for the 25-year-old who won bronze at the Moscow world championships in 2013.
Even though Warner finished with 8,695 – breaking his own national record – he said he still felt some disappointment.
“You’re always fighting for gold but when a guy breaks the world record you can’t complain too much,” he said. “I’ve got a silver medal here in Beijing. I’m moving in the right direction. I’ve had a great season in which I’ve broken the national record twice.”
He added: “But seeing Ashton run an incredible time in the 1500 makes me a little disappointed with my own performance. I tried to get 8,700 points but I didn’t have it in me. I didn’t push myself like I know I could have and I kind of regret that but it keeps you coming back.”
Eaton, who is married to the heptathlete Brianne Theisen-Eaton, praised his wife for her support during the competition.
“I wouldn’t have done what I’ve done without her,” he said. “During each event I was looking for her in the stands. She knows when I’m struggling and it’s good to see her face and to have someone who knows what you’re going through to support you."