Coffin on the Wall

This coffin can be seen perched on top of the perimeter wall of The Priory at Edington in Wiltshire. Someone told me it was the last resting place of a monk who had been ex-communicated and therefore not allowed to be buried within the church. I would love to find out more about it but cannot find any reference to it on any website. Spoke to a few locals who did not even know it existed so they weren't much help!!
Any information gratefully received!