Complex sentence: Richard de Rulos, who was Lord of Deeping Fen during the reign of William the Conqueror erected a strong embankment to prevent flooding of the meadows adjoining the river, which then became fertile fields and a pleasure garden.
Split into simpler sentences: Richard de Rulos, who was Lord of Deeping Fen during the reign of William the Conqueror. He erected a strong embankment to prevent flooding of the meadows adjoining the river, which then became fertile fields and a pleasure garden.