Standing in the packed crowd, cheering the runners on, I felt a slight pang of guilt. Should that be me out there, I thought? Should I be in trainers and shorts, drenched in sweat, with a face like somebody having a Tabasco colonic? I glanced around me, at the spectators with their big smiles and sun hats and cans of Strongbow Dark Fruit cider, and decided that, no, it’s probably best that I’m on this side of the fence.