And there is more: what we see on a map is only the half of it. A river no more begins at its source than a story begins with the first page. Take Trewsbury Mead, for instance. That photograph, do you remember? The one they were so quick to dismiss, because it wasn't picturesque? An ordinary ash in an ordinary field, they said, and so it appears, but look more closely. See this indentation in the ground, at the foot of the tree? See how it is the beginning of a furrow, shallow, narrow, and unremarkable, that runs away from the tree and out of the picture altogether? See here, in the dip, where something catches the light and shows as a few ragged patches of silver in the grey shades of muddy soil? Those bright marks are water, seeing sunlight for the first time in what might be a very long time. It comes from underground, where, in all the