 In his capacity as Surveyor of the Navy, Walker specified the requirements that led to the design of the large wooden screw frigates HMS "Diadem", HMS "Doris", HMS "Ariadne", HMS "Galatea", HMS "Mersey", and HMS "Orlando" which were known simply as "Walker's Big Frigates".These large vessels were designed to compete with the United States Navy which had decided to build five steam frigates and one steam corvette.The ships had only a short service history as they were both too large for wooden ships and expensive to operate, as they required large crews.