Polruan sits at the mouth of the Fowey estuary and If you look closely on the right of the photo you will see the defensive block house which dates back to the 14th centaury and has a matching twin on the other side of the estuary at Fowey. There was a chain strung between the two towers to prevent any Dutch, French or Spanish attackers from entering the river. The chain could be lowered to allow access to local shipping.
