I have gone back in time to a landscape not seen in this part of the world for the best part of 500 years. All around me are signs of intensive engineering – not by humans, but by beavers .

Mark Elliott at the Devon Wildlife Trust is showing me round 2.8 hectares of wetland on the edge of Dartmoor, UK. In 2011 the trust released a pair of Eurasian beavers here. “They’re really busy at the moment,” he says.

Before the release, the area was a scrubby woodland …