In a tree-lined car park, just before sunrise, a few birds were starting to sing. This was the beginning of my National Trust dawn walk at Sissinghurst Castle in Kent.

The chorus swelled with the first light. Our ornithological guides, Fred O’Hare and Peter Dear – decked out in hats with ear-flaps pinned back – began the stroll around the estate. Their first spot was a group of starlings on the tiled, conical roofs of some oast houses.