OK,so its not one of the famous walled castles,like nearby Framlingham,but this was the reality of life in a foreign land.The Normans invaded and conquered,but it took a long time before ditches and water filled moats weren't a necessity.It seems this site never was rebuilt in stone,just maintaining a wooden stockade on the inside of a moat.
see http://www.castlefacts.info/castledetails/castleDetails3.aspx?uin=13386