Kenyan world record holder Eliud Kipchoge has announced he will make another attempt at becoming the first man to run a marathon in under two hours.
His latest effort to push the endurance boundary will likely take place in Britain later this year, in a project backed by Jim Ratcliffe, the billionaire owner of chemical firm INEOS.
Kipchoge revealed the race plan at the Iffley Road running track in Oxford, where Briton Roger Bannister became the first man to break four minutes for the mile 65 years ago on Monday.
"This would really surpass everything because this will go down in history as far as the human family is concerned," the Kenyan said.
"It is not about recognition or ratification but to make history and to pass on a message that no human is limited. Running the fastest-ever marathon of 2:00.25 was the proudest moment of my career."
Kipchoge achieved that feat in his "Breaking Two" project on Italy's Monza motor racing circuit in 2017, though the time was not ratified for record purposes because he used "in and out" pacemakers and a moving drinks station.
But last year he did lower the legal world record for the marathon by an astonishing 78 seconds when posting 2:01.39 in Berlin, and in April he ran the second-fastest time in history to win the London marathon in 2:02.37, a victory that took his astonishing record to 11 wins from 12 races over the 26.2 mile distance.
Breaking two hours would now appear to be the only thing missing from the CV of the former Olympic champion ranked among the greatest his sport has seen.
Some details for Kipchoge's latest record attempt are still to be ironed out, but the so-called "1.59 Challenge" is likely to take place in September or October on a two to three-km course possibly in one of London's Royal parks.
The last great barrier in modern athletics, and the greatest marathon runner of all time.
— INEOS 1:59 Challenge (@INEOS159) May 5, 2019
Eliud Kipchoge will attempt to break the two-hour barrier in the INEOS 1:59 Challenge later this year.
No human is limited.#INEOS159https://t.co/VwMG785yfK pic.twitter.com/ERZTQuKdMb
It will again be un-ratified as the Kenyan will use a squad of pacemakers, dipping in and out of the race so that they can maintain the phenomenal two minute, 50 seconds per km pace necessary.
Although Nike is not spearheading the attempt as it did in Monza, Kipchoge, 34, will again wear their somewhat controversial carbon-insoled Vaporfly shoes.
Nike says the shoes, which have been passed legal by the sport's governing body the IAAF, improve running economy by up to four percent, though some critics say they give such an advantage that without them Kipchoge would be a "routine" 2.03 or 2.04 performer.
The shoes, pacemakers, a wind-blocking pace-clock car and rolling drinks stations helped take Kipchoge agonisingly close to the target in Monza and the runner says the lessons learned then will make him even more likely to pull off the record.
Since then Kipchoge has massively improved his best legal time and now believes a change in mentality can help him maintain the necessary pace to break two hours.
Ratcliffe, 66 and a keen runner for decades, said that the missing link could be a crowd to watch and encourage, after the Monza attempt took place in front of a handful of media, sponsors and associates.
"If Eliud has got a fantastic crowd cheering him on, it's going to make a bit of difference and we don't need to make a lot of difference to make up 26 seconds," he said.
"I was in the pace car in front of Eliud for the London Marathon and he was looking very serene and comfortable. He's still getting better."
Ratcliffe has taken over ownership of cycling's former Team Sky, funded Ben Ainslie's 2021 America's Cup sailing challenge and owns Swiss soccer club Lausanne Sport.
"It's good fun. We make billions in profits so what's wrong with investing a bit of that in sport, in good challenges, good people?," he said. "Eliud is the finest marathon runner there has ever been and I think it will be very inspirational, to get kids putting running shoes on.
"It would be an extraordinary achievement. It's almost super-human, isn't it really? To break two hours in a marathon is quite unthinkable."