On Boxing Day 2009 at Kempton Park, Kauto Star attempted to win his fourth consecutive King George VI Chase. He jumped well throughout the race and went clear with three fences to jump, then easily drew clear to win by 36 lengths. The margin of victory set a new record in the race, breaking Arkle's 44-year-old record of 30 lengths, and directly leading to the rule change dispensing with the traditional winning distance of "a distance" which had previously been used for wins of more than 30 lengths.
In winning the race, Kauto Star was awarded a Racing Post Rating of 192, the highest ever earned by a National Hunt horse. He was given a Timeform rating of 191, the highest given to a horse in almost 40 years and making him the joint-third highest-rated steeplechaser of all time, level with Mill House and behind only Arkle (212) and Flyingbolt (210). He was also officially rated 193, the highest ever awarded to a chaser.