Indeed interesting, and it does not surprise me that a human can beat a animal carrying a heavy load (a human) in an endurance event given we are hairless sweaty mammals optimised for endurance rather than speed. Adding a proportional burden for humans (maybe 10kg) would give horses a huge advantage.<p>It seems the race is also long-term optimised for humans to win. There are a lot more human competitors (> 10:1 ratio). The prize fund increased by 1000 pounds per year until a human won, no doubt attracting faster and faster athletes in increasing numbers.<p>The course has also been varied making year on year comparisons difficult.
It also appears that the horses are given what appears to be a 15 minutes handicap under the guise of 'vet checks'. (Commentary is there under the history section of the article)<p>I couldn't find more information on whether there are other things done to favor human over the house.