It started as a pub bet. Who would win? Man or horse? The riders dominated for ages before a Royal Marine who trained specifically for the event put one back over the animal kingdom a few years ago by winning. The humans get a head start.
They've also introduced mountain bikers of late and they tend to win hands down but don't get taken as seriously.
The ex did this once in one of her many slightly crazy athletic endeavours.
PS I appreciate this is late, hadn't seen it before.