I pushed through the blackthorn hedge and found myself standing on the bank of a rippling pool. When I came here last summer, this was dry land; where had the pond come from? I’d stumbled upon what is known as a ghost pond. A ghost pond is one of the estimated million pools that Britain has lost in the last century. These modest-sized meres were once used for watering plough horses, powering mills and stocking fish, but when workhorses and water mills disappeared from the landscape, so did the ponds.