The top runners are amazing athletes too. In the late 80s Kenny Stuart finished his career on the fells and had a go at road marathons. 2h11m. Not too shabby. Andy Davies came from the fells and has run sub 2h20m recently.
I’d also second the Feet in the Clouds rec. Great book. It looks likely Kilian Jornet is going to have a go at the Bob Graham this year, presumably to have a crack at the record. It’s stood for 35 years.