Off the far tip of Cornwall, beyond Land's End, lie the Isles of Scilly. On some of the islands live the famous Scilly Shrews. In the equally famous Abbey Gardens on Tresco, there is a big shed in which humans have put figureheads from their ships. Behind that shed, somewhere in the long grass, is a nest containing one particular family of shrews. There's Mum (whose real name is Hepzibah),...