Improbable walls

The Yorkshire Dales are famed for the drystone walls that snake across the countryside. Ribblesdale is no exception and here the local limestone gives characteristically lumpy and quite light-coloured walls. I always marvel at the improbable constructions - tumbling down over crags or meandering round as if built by a drunkard. I often find myself asking... why on earth was that built there? Why is it that shape? Who built it in the first place? How old is it? Those questions never get answered but that doesn't stop me wondering.