More photos of Durham here, but I am far from having finished the upload!
Update: the knocker on the door is a replica. The real knocker is in the cathedral’s Treasury. It dates back to the MiddleAges
Durham Cathedral was also a centre for criminals seeking sanctuary. A criminal would bang the sanctuary knocker at the north door on Palace Green to alert one of the watchmen. They would be admitted into the cathedral, and offered sanctuary for 37 days. They were obliged to confess the details of their crime to the coroner, and they had to change their clothes for a black robe with a yellow cross on the shoulder.
From BBC h2g2