Eliud Kipchoge achieved a historic breakthrough today - although not an official world record – as he became the first man to better two hours for the marathon distance, clocking a time of 1 hour 59min 40.2sec.
On a painstakingly selected flat course in Vienna, the 34-year-old Kenyan finished the INEOS 1:59 Challenge alone, having waited until the final 500 metres to move through the phalanx of pacers who had shielded and supported him in shifts throughout a race that had begun at 08.15am and ended, significantly, before 10.15.
As this normally reserved athlete pointed the way forward to his own meeting with athletics history, before then pointing at his eyes, almost as if to say "Can we believe this?", the final group of seven from the 35 pacers who had assisted him had turned into cheerleaders and supporters, their dark kit contrasting with the white of the man of the moment.
The crowds had come in large numbers to this flat run through the famous Prater park, where horse chestnut trees on either side had done their bit to offer shelter in what was effectively a combined operation of hi-tech and human endeavour.
The first person Kipchoge greeted after the line was his wife, Grace, who was present with their three children to watch her husband achieve the kind of athletics landmark created by Roger Bannister's sub four-minute mile in 1954.
"I'm feeling good," said the Rio 2016 champion at the finish, shortly before being mobbed by his pacers and supporters.
"After Roger Bannister made history, it took me another 65 years. I've tried but I've done it.
"I have run under two hours, in order to inspire people. and to tell people that no human is limited.
"You can do it.
"I am expecting more of athletes all over the world to run under two hours after today."
Asked about how the task felt on the road, where the pacing car in front of the group had thrown down green laser lines to indicate the pace required, he responded:
"It was two hours - it felt like 20 minutes.
"The pacemakers are among the best in the world.
"I want to say thank you to them for accepting the job.
"We made this together."
Later, referring to his final run-in, he added: "That was the best moment of my life - the time I knew I was going to make history."
In May 2017, Kipchoge attempted to run a sub-two-hour marathon in similar assisted circumstances as part of "Nike’s Breaking2 Project" at the Monza racing circuit and clocked 2:00:25 - just 26 seconds short of his quest.
Through halfway, the runners were right on pace, coming through at 59:35, well ahead of Kipchoge’s 59:57 half at Monza in 2017.
Kipchoge, who has run 12 of his 13 normal marathons, holds the official world record of 2:01:39, set in winning last year's Berlin Marathon, and Ethiopia's Kenenisa Bekele ran 2:01:41 in the German capital last month.
Three factors meant this could not be an official world record - there were no other racers, Kipchoge was being regularly handed drinks, and he was surrounded at all times by pacers, interchanging every three kilometres, in a formation best calculated to shield him from any wind.
They formed a V formation in front of him, with a key runner - or captain - directly in front of him, and two runners slightly behind him.
The runners were wearing versions of the new Nike Vaporfly trainer, which aids performance with carbon plate and huge foam midsole.
Kipchoge was wearing a previously unseen version.
The meteorologists involved in the project decided a start at 8.15am local time was the best in terms of conditions, and as the groups of pacers switched in and out, Kipchoge never fell outside the target time, with the target kilometre time of 2min 50sec being regularly achieved or bettered.
The quickest kilometre split was 2min 48sec; the slowest 2min 52sec.
It was the equivalent of running a 400 metres in 68 seconds, 105 times over, requiring an average speed of around 14mph, or 21kph.
The line-up of 41 pacemakers - six were standing by as reserves - included Ethiopia's World Championships 5,000 metres silver medallist Selemon Barega, former world 1500m and 5,000m champion Bernard Lagat of the United States, a longstanding friend of Kipchoge's, who was one of the designated "captains", and Norway's Ingebrigtsen brothers - Henrik, Filip and Jakob.
Kipchoge started his effort on Vienna's famous imperial bridge, the Reichsbrücke.
After approximately 1.2 kilometres he reached the Ferris Wheel at the Praterstern roundabout, where he entered the Prater and begin 4.4 laps of the tree-lined Hauptallee, the historic avenue that runs through the heart of the Viennese Park.
A total of 30 broadcasters aired the event live in over 200 territories across the world.
Major deals include BBC, who streamed the Challenge live digitally in the UK, NBC, who aired the live stream digitally on their Olympic Channel and replayed it on their linear channel, NBC Sports Network in the US, and Eurosport, who were live on Eurosport 2 in 54 countries in Europe and 12 countries throughout Asia-Pacific, as well as streaming live on their website.
Alongside the terrestrial broadcast deals, the INEOS 1:59 Challenge had agreed a partnership with YouTube, who streamed the entire live broadcast of the event, being delivered by the British independent award-winning TV sports production and media company Sunset+Vine.
The You Tube streaming had attracted more than 750,000 viewers by the closing stages.
The INEOS 1:59 Challenge was supported by Sir Jim Ratcliffe, reportedly Britain’s richest man, and his petrochemical company Ineos, which has recently taken over cycling's Team Sky and is funding Sir Ben Ainslie's next America's Cup sailing bid.