To the north-east of the church, within the boundaries of the Roman fort, are the remains of Bewcastle Castle, an ancient castle built in about 1092, using stones from the Roman fort. The castle was reputedly destroyed by Oliver Cromwell in 1641.

Interestingly the field next to the church is called "the Cannon Field" to this day. Several years ago metal detectorist unearthed a cannon ball about the size of a cricket ball right here, lending weight to the idea that Cromwell laid seige here indeed.