If, on a winter’s day when the wind is up, you find yourself in search of something, but not entirely sure what that something is, go and find a copse of young deciduous trees. It is important that they are growing close together; a small thicket of self-set saplings is best, of a kind you’d find in unmanaged woodland or derelict lots.

Then press your ear against one of the trunks, and wait, and listen.