I don't know about the stone I'm afraid. But I do notice that the Rev exorcised a Black Dog somewhere and even had a go at the Loch Ness Monster. Poor things. I feel like phoning the RSPCA, it just isn't on.
Yeah, the Black Dog was at Kettleness on the Yorkshire coast.
The same place that Dracula came ashore in Stoker's novel, as a black dog. Omand's got a few vampiric strands running through his exorcising tales.
Andy Roberts tried to track it down when he was writing 'Ghosts and Legends of Yorkshire' but drew a blank. He reckons it's probably a castle somewhere in North Yorkshire...