Nennuis was a supposed Catholic Bishop/Historian who wrote of the covenants between the Druids and the Christians about the 6th century.
John Hugh suggests in his writings that he found his tomb...? The Stone Door:
"...when I discovered this book in the underground chamber in that old mansion long ago, I gazed with wonder on his bones still parly in the stone chair, where he had penned these words long ago. There were worn tatters of his vestments also there and other things proving that he was in "Holy Order". The cause of this man's death was his disregard of 'the key'....etc"

Illustrated by Leo del Pasqua from Ottawa

for the manuscript of the same name by John Hugh Roberts