It’s true that many of the books which include the tale make the legend sound almost feasible . . . but not to a truly cynical mind. For one example, look at the little booklet Dartmoor Legends Retold – vol. II by T.H. Gant and W.L. Copley, published by Baron Jay. I picked this story as the start point for my novel because it offers an attractive amount of detail – the name of the Abbot of Tavistock of the time (Walter), the fact that there was a dispute with the monks of Plymstock Abbey (I changed this to Buckfast because I can find no record of an abbey in Plymstock) and the name of the leading protagonist, Milbrosa. However, lest there be any doubt, I personally do not believe that the legend as retold here has any historical validity. It is a curiosity, nothing more. In some ways this story shows the extreme difficulty of being accurate when you are writing historical works. While it is possible that somewhere amongst the old Abbey papers a record of the event exists, I seriously doubt it.
What do You think about The Devil's Acolyte (2002)?