Emmanuel Wanyonyi went close to breaking David Rudisha's vaunted 800m world record in Thursday's Diamond League meet in Lausanne in what was a mixed night for Olympic champions making their return after the Paris Games.
Wanyonyi repeated the blistering form that saw him win in the French capital, going within 0.20 seconds of the 1min 40.91sec world record set by Rudisha when winning Olympic gold in London in 2012.
The Kenyan will have another chance at the next meet on the elite calendar, in Silesia, Poland on Sunday.
Other Olympic champions who were successful included Botswana's Letsile Tebogo, who blasted to an impressive 19.64sec to win the 200m.
The 21-year-old, whose 200m gold in Paris was the first ever for his country, admitted that he had come to Lausanne on the back of eight days of no training, having made a rapturous return to Gaborone.
"The most important thing for me is that even after such achievements like the ones I did at the Olympics, at the end of the day, you just have to keep running to maintain the form throughout the season," he said.
Greece's Miltiadis Tentoglou left it late to win the long jump in 8.06m and Ukraine's Yaroslava Mahuchikh claimed victory in the women's high jump in 1.99m.
- Revenge for Ingebrigtsen -
It was not all good news for newly-crowned Olympic champions, however, with Grant Holloway, Cole Hocker and German shot putter Yemisi Ogunleye all failing to back up their Paris form by topping the Swiss podium.
There was at least some redemption for Norway's Jakob Ingebrigtsen in beating Hocker in the 1500m.
The Norwegian had been an odds-on favourite for Olympic gold in Paris, but set out too quickly and eventually finished fourth.
"It's been almost two weeks since Paris so there was plenty of time to recover," Ingebrigtsen said of his win in a meet record of 3min 27.83sec.
"For me a lot of it has been mental including going home, taking some easy days and then getting back to work. Tonight's race gave me good answers."
Perhaps the biggest upset was in the men's 110m hurdles as Olympic champion and three-time world gold medallist Holloway was edged into second by Jamaica's Rasheed Broadbell, who won in 13.10sec.
"Coming off that high from the Olympics, it's challenging to keep that same pace, but I'm focused on learning from this race to run better next time," Holloway said.
"Once you've reached your goals, it can be though to keep pushing, but I'm prepared to defend my world titles. As long as I'm improving, it's a good sign."
- Two-lap delight -
One of the events of the season has been, without doubt, the men's 800m, with four athletes in the Olympic final dipping under the 1min 42sec mark for the first time ever.
And once again it did not disappoint in Lausanne as Wanyonyi of Kenya set a sensational world lead of 1:41.11 for victory.
It was the joint second fastest time ever run -- alongside Denmark's Wilson Kipketer.
Aided by wavelength technology and two pace-setters, Wanyonyi gritted his teeth right through to the line, with Rudisha's once-untouchable mark seemingly on course to be broken at some time in the near future.
Wanyonyi will not be resting on his laurels, however, heading straight to Poland for Sunday's Diamond League meet, while also due to compete in next month's finals in Brussels.
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"I'm so happy to have run the world lead today in Lausanne," said Wanyonyi.
"My body is moving very well. I got up to come here and told my body 'you can do something for me, I need to run very fast'."
France's Gabriel Tual, who finished third behind Wanyonyi and Canada's world champion Marco Arop, said he didn't think Rudisha's record would stand for much longer.
"When you see the wavelength light just in front, it's really not far," he said. "I think it'll be broken either in Silesia or Brussels."
Another winner in the Swiss city meet, coming just 12 days after the last of the track and field action at the Stade de France, was Femke Bol.
The Dutchwoman won the 400m hurdles in 52.55sec to compensate somewhat for her bronze medal showing in Paris behind record-setting Sydney McLaughlin-Levrone and Anna Cockrell.
