An English market town on the Welsh border, Ludlow is small, landlocked and remote. Yet it has more listed buildings than anywhere else its size in Britain; not one, but two Michelin-starred restaurants; and a fairytale castle which was once the capital of Wales. Geographer and adventurer Nicholas Crane discovers how such a cut-off town came to be packed with so many treasures, and asks whether it really is as perfect as it first appears.