Along with two other carved stones (probably not Roman), it sits on the inside window-ledge of the window at the west end of the north aisle, inside the little meetings room divided by glass panels from the bulk of the church.
It appears not to have an inscription but its size and moulding bears much resemblance to other stones found along Hadrian's Wall which record the particular centurial unit involved with building or maintaining a specific length of the Wall's fabric.