Eliud Kipchoge has run the quickest recorded marathon on Saturday, crossing the line on the Monza Formula One track in two hours and 25 seconds but missing out on an attempt to break the two-hour barrier.
The 32-year-old's time smashed the official mark of 2:02.57 set by fellow Kenyan Dennis Kimetto in Berlin in 2014 but will not enter the record books largely due to a system of pacemaking not recognised by the IAAF.
The event's sponsor, sportswear group Nike, initially gave the time as 2:00.24 but later revised it up by a second.
"My mind was on under-two hours but in the last two laps I fell 10 seconds behind the pace," the Olympic champion said.
"This journey has been good, it has been hard, it has been seven months hard preparation. It has been history in the world of sport."
"I am happy to have done it in two hours," Kipchoge added.
Kipchoge and the event's only other competitors, Eritrean Zersenay Tadese and Ethiopian Lelisa Desisaran, ran behind an arrow-head of pace-setters, to reduce drag, and a car beaming a green line on the road behind it to show the required speed for the sub-two hours target.
Amid deep scepticism, Nike pitched the attempt as sport's "moon shot", with a keen eye on sales of its running shoes.
It designed a lightweight shoe, Zoom Vaporfly Elite, with carbon-fibre in-sole as part of the meticulous preparations.
The race began in pre-dawn gloom at a brutal pace behind pacemakers who were world class runners in their own right, including former world champion middle distance runner Bernard Lagat of the United States.
The sub-two hour mark required a pace below four minutes and 35 seconds per mile, which the determined Kipchoge managed to stick to until falling behind the pace car in the last two laps of the 2.4 km circuit.
The youngest competitor, 26-year-old Desisa, fell off the pace first and finished in 2:14:10, followed by Tadese in 2:06:51.