There was a to-do by the castle moat this morning, a Common Gull yelling and dive-bombing something in the reeds. We went closer, watching from the other side of the water. A minute later, a young heron flapped up like some improbable homemade construction of feather and wire and bayonet.

The shrieking gull scythed down again. The heron perched on the gate of the footbridge, hunched, tilted back its head until the long spike of its beak was vertical, a grim invitation to the gull to disembowel itself in one of its swooping attacks.

The gull’s dives became shallower, less daring. It withdrew to the ramparts, made one final token aerial assault, then flew off with an angry mutteration of yelps.

The heron lowered its beak, watched us with one golden eye.