His enthusiasm led him to immerse himself in the culture and history of the sport, and eventually to publish a book, Feet in the Clouds, which has become something of a cult among runners and outdoor enthusiasts. It also led him into a series of increasingly severe fell-running challenges, from the classic races (Grasmere, Burnsall, Borrowdale, Ben Nevis) to, ultimately, what many consider to be the toughest challenge of all: the Bob Graham Round, a non-stop circuit of 42 of the Lake District's highest peaks, to be completed within 24 hours.