Not since the days of the first sub-four-minute mile has one barrier attracted so much focus in the world of athletics, but talk of the first sub-two-hour marathon has reignited after Eliud Kipchoge's 2:01:39 run at the Berlin Marathon on Sunday.
The 33-year-old Kenyan ran alone for the final 17 kilometres of the race in the German capital but his pace increased as the race went on.
After covering the first half in 1:01:06, Kipchoge ran 1:00:33 for the final 13.1 miles to take one minute and 18 seconds off the marathon world record set by Dennis Kimetto in 2014.
It was the single biggest improvement on a men?s marathon world record for 51 years. An improvement of just 100 seconds more is now needed for the first sub-two-hour marathon.
Since bursting on to the scene as an 18-year-old at the 2003 IAAF World Championships in Paris, Kipchoge has charted his career path with precision, proving to be not only an indomitable spirit but also one of the most versatile distance runners of his generation.
But his successes on the roads may not have happened had it not been for a pivotal moment in his track career in 2012.
Kipchoge finished seventh in the Kenyan trial 10,000m race at the IAAF Diamond League meeting in Eugene that year, then finished in the same position three weeks later in the 5000m at the Kenyan Trials.
Aged 27 at the time, and having earned bronze in 2004 and silver in 2008, Kipchoge had missed out on a third Olympic appearance.
It influenced his decision to move to the roads, though, and he immediately showed promise. He clocked 59:25 on his half marathon debut in Lille in September 2012 and went on to represent Kenya at the IAAF World Half Marathon Championships in Kavarna later that year, placing sixth.
He moved up in distance again and won the Hamburg Marathon in April 2013 in 2:05:30, the sixth fastest marathon debut in history at that time.
Five months later he improved his marathon PB to 2:04:05 to finish second in Berlin in a race in which Wilson Kipsang broke the world record. It was to be Kipchoge's last and, to date, only defeat in a marathon.
Now a fully-fledged marathon runner, Eliud Kipchoge has gone on to record victories in Rotterdam, Chicago, London (three times) and Berlin (also three times).
In between his second victories in the British and German capitals, Kipchoge also won the Olympic title in Rio, more than making up for the disappointment of missing the 2012 Games.
Up until September 2018, the one accolade that had so far eluded Kipchoge was the world record. But a faultless 2:01:39 run in Berlin saw Kipchoge smash the mark by one minute and 18 seconds.
But it's not just his run of victories that sets Kipchoge apart, it?s also his string of fast times. He has run 2:04:00 or faster on four occasions and 2:05:00 or faster on nine occasions ? and that?s not including his 2:00:25 clocking in Monza in an experimental and unofficial race.
Now aged 33 and after racing internationally for 16 years, Kipchoge is showing no signs of slowing down for the 26.2-mile distance.
Kipchoge's career achievements
2002 World Cross Country Championships - U20 race, 5th
2003 World Cross Country Championships - U20 race, 1st
2003 World Championships - 5000m, 1st
2004 World Cross Country Championships - senior race, 4th
2004 Olympic Games - 5000m, 3rd
2005 World Cross Country Championships - senior race, 5th
2005 World Championships - 5000m, 4th
2006 World Indoor Championships - 3000m, 3rd
2007 World Championships - 5000m, 2nd
2008 Olympic Games - 5000m, 2nd
2009 World Championships - 5000m, 5th
2011 World Championships - 5000m, 7th
2012 World Half Marathon Championships, 6th
2016 Olympic Games - marathon, 1st
Kipchoge's marathon career
1st, 2:05:30 Hamburg, April 2013
2nd, 2:04:05 Berlin, September 2013
1st, 2:05:00 Rotterdam, April 2014
1st, 2:04:11 Chicago, October 2014
1st, 2:04:42 London, April 2015
1st, 2:04:00 Berlin, September 2015
1st, 2:03:05 London, April 2016
1st, 2:08:44 Rio (Olympic Games), August 2016
1st, 2:03:32 Berlin, September 2017
1st, 2:04:17 London, April 2018
1st, 2:01:39 Berlin, September 2018
Marathon world record progression
2:12:00 Morio Shigematsu (JPN) Chiswick 1965
2:09:36.4 Derek Clayton (AUS) Fukuoka 1967
2:08:33.6 Derek Clayton (AUS) Antwerpen 1969
2:08:18 Rob de Castella (AUS) Fukuoka 1981
2:08:05 Steve Jones (GBR) Chicago 1984
2:07:12 Carlos Lopes (POR) Rotterdam 1985
2:06:50 Belayneh Densimo (ETH) Rotterdam 1988
2:06:05 Ronaldo da Costa (BRA) Berlin 1998
2:05:42 Khalid Khannouchi (MAR) Chicago 1999
2:05:38 Khalid Khannouchi (USA) London 2002
2:04:55 Paul Tergat (KEN) Berlin 2003
2:04:26 Haile Gebrselassie (ETH) Berlin 2007
2:03:59 Haile Gebrselassie (ETH) Berlin 2008
2:03:38 Patrick Makau (KEN) Berlin 2011
2:03:23 Wilson Kipsang (KEN) Berlin 2013
2:02:57 Dennis Kimetto (KEN) Berlin 2014
2:01:39 Eliud Kipchoge (KEN) Berlin 2018