Marathon from the start at Windsor Castle to the royal entrance to the White City Stadium, followed by a lap (586 yards 2 feet; 536 m) of the track, finishing in front of the Royal Box. The course was later altered to use a different entrance to the stadium, followed by a partial lap of 385 yards to the same finish. The modern standard distance for the marathon was set by the International Amateur Athletic Federation (IAAF) in May 1921 directly from the length used at the 1908 Summer Olympics in London. An official IAAF marathon course is 42.195 km (42
2012 Olympic Marathon Course as 42.195 km and specifically state that the course must not be less than this distance. The rules further state that in Olympic competition the standard distance may not be exceeded by more than 0.1%. In order for a marathon performance to be ratified as a world record by the IAAF, the course must also meet other criteria that rule-out "artificially fast times" produced on courses aided by downhill slope or tailwind: the distance between start and end points when measured in a straight line should not exceed 50% of the length of the course (21.092 km in the case