Yesterday, I began reading Robert MacFarlane's wonderful new book, The Underland. In the first chapter, the author and a friend enter a labyrinth of caves through a pothole. This morning, by astonishing coincidence, up pops this photograph of a Yorkshire fluted pothole at the British Geograph site. I visit Geograph every morning and sometimes pull together three or four photographs to prompt ideas for a story. This one is suggestive, for sure.