The dog walker looked confused. ‘The reaves? I’m sorry. I’ve no idea what they are.’ He spoke with the kind of Devon accent that indicated a lifetime spent out on the hills of Dartmoor. ‘But, if it’s the Bronze Age settlement you’re looking for, then it’s up there on the top of that there hill,’ he said, pointing towards the summit of a boggy hillside swept in cold drizzle.

Following the direction in which he had pointed, I started trudging up the slope, my boots squelching in the ever-present Dartmoor mud. As I walked, I realised that the heathery trail I was following was running between two barely discernible ridges of grass, out of which poked the occasional grey granite rock. At first, I assumed this was just the natural lay of the land, but as I looked more closely, I realised that the whole hillside was covered in almost perfectly straight ridges, which fanned out from the Bronze Age stone circles crowning the hilltop. This, I realised, was no natural feature of the landscape. What I was looking at were the reaves. Built by Bronze Age hands, they are all that’s left of some of the world’s oldest hedges.