I've always found my best ideas while walking or riding my bike, and yet I've never really felt comfortable about going for a long walk on a day when I'm meant to be writing. It just doesn't feel like work, even though I know I get more done in an hour sitting on my bike or tramping around the edges of ploughed fields than I do in five hours sitting in front of the computer screen. I'm experimenting this year, and it seems to be true that the more I walk the better I write. It may just be coincidence, but I'll keep my fingers crossed.
Some years ago I was given this wonderful book by Morris Marples which introduced me to, among others, 'the Odcombian Leg-stretcher' Thomas Coryate who in 1608 walked from Somerset to Venice and back. And walking twenty miles and back to visit a friend meant nothing to Wordsworth and Coleridge! Get hold of the book if you can - it's a great read.