Eliud Kipchoge has become the first athlete in history to run a sub two-hour marathon after shattering the record by 20 seconds.
The Kenyan, who already holds the official world record, began his effort at 7.15 BST in Vienna on Saturday morning.
He was greeted with a misty autumnal morning and a smattering of fans on Saturday for his bid to run an unofficial sub-two hour marathon.
The 34-year-old marathon world record holder completed the first 21 kilometres in 59.35 minutes, 11 seconds under the two-hour pace. However, there were a few spots of rain which had not been expected and which could hamper his attempt.
Kipchoge was being guided by rotating seven-man teams of pacemakers, many themselves world class runners, and by an electric pacecar which showed the ideal pace and the position they should be running.
The highly controlled attempt to break the two-hour barrier consists of 4.4 laps of a 9.6 kilometre course, including a long straight with a loop at each end.
The sport’s governing body, the IAAF, will not recognise the run as an official record because it is not in open competition and it uses in and out pacemakers.
Kipchoge, the reigning Olympic champion who set an official world record of 2:01.39 at the Berlin marathon in September last year, missed out by 26 seconds when he previously attempted to break the two-hour barrier in Monza in May 2017, a race run without spectators.
The pacer car fires a fluorescent green laser beam onto the road to mark where he needs to be
They will also follow an electric pace car that emits green lasers to show Kipchoge where he needs to be in order to beat the record.
The laser will actually be set at a time or 20 seconds below the two-hour mark, ensuring that Kipchoge will be ahead of the target and thus not denied his prize by a stumble.
In Monza, the scientific support team was put together by Nike.
This time, British billionaire Sir Jim Ratcliffe, through his company Ineos, is funding Kipchoge’s shot at history.
As in Monza, Kipchoge is running in the Vaporfly, a Nike shoe containing a highly controversial carbon-fibre plate in the soles, supposedly capable of improving times by one per cent over any other shoe.
Kipchoge ranks the ‘sub-two’ – one of sport’s great unconquered frontiers – as ‘like man landing on the moon’.
This week he said that it would ‘show to the world that when you focus on your goal, when you work hard and when you believe in yourself, anything is possible.’
Last September he ran the distance of 26 miles and 385 yards in the Berlin Marathon just 99 seconds outside the two-hour mark, shattering Kimetto’s record by a minute and 18 seconds. In April, he eased away from Sir Mo Farah soon after crossing Tower Bridge, finishing in 2hr 2min 38sec.