How tough is this race? My 15 year old step daughter is running this, and wants to know how hard it will be. And what the hills and terrain is like. I know Chesham well as I grew up there but I'm not sure where the route will take them, apart from up and back down the park and through Herbert's hole. And I have been on the Fetch site and they say the distance is 10.5k. Are the right?