Complex sentence: The date of Pierre's move to England from France is unknown, but he settled in Shropshire and obtained a position with the powerful noble Hugh de Spencer, eventually becoming High Steward of the latter's Oxfordshire estate.
Split into simpler sentences: The date of Pierre's move to England from France is currently unknown, but he settled in Shropshire upon his arrival. He soon obtained a position with the powerful noble Hugh de Spencer, eventually becoming High Steward of the latter's Oxfordshire estate.