They're considered to be the most persistent of all ghostly animals. Reported sightings of Phantom Black Dogs in Britain date back to medieval times. Four hundred years ago, a devil dog was even blamed for killing five people in a church. Some believe they're protective creatures, others, an omen of death. Whatever their purpose, the Phantom Dogs have left an indelible impression on anyone who's witnessed them. Animal X travelled to East Anglia to speak to those who have witnessed this ghostly phenomenon.