I’ve been unable to cross reference this folklore tale and can find no other references to the lost village of Saint Sulpicus.
Beyond the steel works, on the southern bank of the Tees, close to Paddy’s Island, and buried beneath millions of tons of steel slag, lie the remains of a fort; the last refuge of the Anglo-Saxons who refused to accept William the Conqueror as their king. In 1072 the villagers of Saint Sulpicus, just down the coast betrayed them to the king who led an army from York to attack them. The refugees managed to escape, but the fort was abandoned.
King William rewarded the villagers of Saint Sulpicus by giving them his war helmet, stuff with gold coins. However, before these treacherous wretches could share out their ill-gotten gains, their village was destroyed by divine wrath, a huge storm washing the village and villagers, into the sea. On one night of the year, the souls of these villagers are said to appear on the beach bewailing their fate and desperately searching for their lost gold.
The Haunted Coast