Probably some Druidic/Satanic individual.
Although the story of this Father Benedictus is somewhat interesting. There's a credible report of two American tourists in 1932 who were trying to make the rounds at Westminster Abbey before closing and then started to panic as they feared that had been locked inside. At that point, a hooded figure who identified himself as "Benedictus" showed them an alternative way out. They reported that he spoke a peculiar (very elegant) dialect of English. When they went back the following day to thank him, they were informed that there was no "Benedictus" at Westminster Abbey. There were in fact Benedictine monks there during the time of Henry VIII, but none in recent years.