In 1960, because US-designed missiles were seen at the time to be superior to the Seaslug, the Royal Australian Navy (RAN) proposed a variation of the County-class armed with the US Tartar missile and two additional modifications: hangar space for three Westland Wessex helicopters and a steam propulsion system, rather than the combined steam and gas system used in the County class. However, the RAN instead decided to proceed with the (a modified version of the US ). Two different reasons have been put forward for the Australian decision: according to an Australian history, British authorities would not allow a steam-propelled variant of the county, whereas, according to a British account, the re-design required to accommodate the Tartar missile would have taken longer than the RAN was prepared to accept.