Uganda’s Joshua Cheptegei produced an astonishing run in Monaco to break the 16-year-old 5,000m world record by almost two seconds.
The 23-year-old, who won the 10,000m world title in Doha last year, had promised he would take a shot at the time but success seemed unlikely.
However, guided by trackside lights illustrating world record pace, he came home in 12 minutes 35.36 seconds.
The previous mark, set by Ethiopian great Kenenisa Bekele, was 12:37.35.
Remarkably it is Cheptegei’s second world record in Monaco this year, despite the season being badly disrupted by the coronavirus pandemic.
He broke the 5km road world record in the principality in February..
“Monaco is a special place and it’s one of these places where I could break the world record,” he said.
“It took a lot to keep being motivated this year because so many people are staying at home but you have to stay motivated.”
Elsewhere, world champion Noah Lyles showed his quality in the 200m with a commanding victory in 19.72 seconds. His younger brother Josephus was second on his Diamond League debut ahead of fourth-placed Adam Gemili of Britain in 20.68 seconds.
Katarina Johnson-Thompson, who won heptathlon world gold last year, admitted she was “not in the best shape” after finishing sixth in the high jump with 1.84m, 14cm short of her personal best.
Cheptegei was not the only athlete to make light of the lack of competitive action in 2020 to post impressive times.
Britain’s Laura Muir broke Dame Kelly Holmes’ 21-year-old British 1,000m record with a time of 2:30.82, in a race won by Kenya’s Olympic champion Faith Kipyegon in the second fastest time in history.