Hedingham Castle in Braintree

You're standing at Hedingham Castle, in the little village of Castle Hedingham in Essex. Look up at that almost square stone tower. That's the keep, built around 1140, and it's often called the best preserved Norman keep in England. It rises more than twenty-one metres, and at the base the walls are about three and a half metres thick. The core is flint rubble and lime mortar. The outside, though, is faced with neat blocks of stone hauled all the way from a quarry in Barnack, Northamptonshire. For an Essex castle, that's really unusual.