Walking the final miles of the South Downs with the artist Chris Drury, Robert Macfarlane explores the sometimes eerie relationship between walking, collecting, and creation. Vladimir Nabokov, Iris Murdoch, Hugh MacDiarmid, Bruce Chatwin, and Drury's own remarkable land-art sculptures feature, as does the life and death of Virginia Woolf, who drowned herself in the Sussex Ouse having slipped a single, heavy flint into her pocket. Producer Tim Dee.