Chillingham Castle in Northumberland

You're standing at Chillingham Castle, a medieval castle in the north of Northumberland. Have a look at its shape. It's built around a square courtyard, with battlements running along the top of the walls. In places those walls are about twelve feet thick. That wasn't overkill. You're close to the old border between England and Scotland, two nations that were at each other's throats for centuries.