Maybe it was Blanchland Abbey - Scots instead of Romans though?
The abbey granges were pillaged during the anglo-scots wars, in particular during 1327, but the abbey itself was apparently left unscathed. There is however a legend that during one raid in the area, the monks prayed that the abbey would be spared. Subsequently, a mist descended which shielded the valley and monastery from view and was overlooked by the Scottish raiders, who passed by. The foolish monks upon hearing this, proceeded to ring the abbey bells to signal to every one in the valley that it was safe, that the invaders had passed. During their celebration of bell ringing, the Scottish invaders heard the bells, turned around and ransacked the Monastery.