The Sanctuary Knocker
In medieval times, those who “had committed a great offence”, such as murder in self-defence, could grasp this and be given 37 days of sanctuary within the Cathedral. If they couldn't come to an agreement with their accuser they would face trial or have to leave the country.
This is the original made around 1155. A replica now hangs on the North Door. The design is based on an Anglo-Saxon version of 'hell-mouth', as in the entrance to hell. If you look closely, you can make out a man being eaten by a lion, which is being eaten by a double-headed snake. It was meant to be hideous enough to ward off evil spirits.