Clayton set a marathon world best in the Fukuoka Marathon, Japan on 3 December 1967 in 2:09:36.4, in what is considered a classic race, the first marathon race ever run in less than two hours and ten minutes.
He went on to break this time in Antwerp on 30 May 1969 by more than a minute; this time stood as the world best for nearly another 12 years.[nb 1] His personal best time of 2:08:33.6 is still a world class marathon time. Clayton represented Australia at the 1968 Summer Olympics in Mexico City, finishing in 7th place (2:27:23). Four years later he finished up in 13th place (2:19:49) in the same event.
At the 1971 Australian Athletics Championships, he won the marathon in 2:11:08.8. Two years later, he won the Australian Athletics Championships marathon again in 2:12:07.6
- The International Association of Athletics Federations has published a progression of road racing world bests and records that were widely recognized prior to ratification and official acceptance by the IAAF. According to that progression, Clayton's 2:08:34 performance in Antwerp on 30 May 1969 was a world best at the time. Other road racing authorities, including the Association of Road Racing Statisticians, consider Clayton's performance to have occurred on a short course and recognize other athletes in the progression for world best in the marathon.
- "12th IAAF World Championships In Athletics: IAAF Statistics Handbook. Berlin 2009" (PDF). Monte Carlo: IAAF Media & Public Relations Department. 2009. pp. 546, 563, 565, 651, and 653. Archived from the original (PDF) on 6 August 2009. Retrieved 15 May 2010.
- Association of Road Racing Statisticians, World Best Progressions- Road. Retrieved 15 May 2010.
- "Derek Clayton". Sport Australia Hall of Fame. Retrieved 10 September 2013.
| Men's Marathon World Record Holder
3 December 1967 – 6 December 1981
Robert de Castella
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