The Welsh Marches, gloriously unvisited amid their wooded hills and swift-flowing streams, have remained mysteriously off-limits to the sort of novelist eager for territorial rights to a particular landscape or locality. Apart from Bruce Chatwin’s On the Black Hill and Mary Webb’s torrid 1920s sagas of heartache and claustrophobia in field and farmhouse, fiction has mostly steered clear of Wye, Teme and Clun and their adjacent mountains.