Cromarty Firth was not identified as a naval anchorage until 1912, presumably then because of the growing concern about the reach of the German Navy. This was to a floating base, in that there would be no shore establishment apart from the fixed defences. These defences were to be three 9.2-inch gun, six 4-inch guns, eight defence electric lights and associated accommodation. The cost was £121.500 with a recurrent budget of £15,00. The low capital cost was probably dues to the reuse of existing naval guns as armament. Unusually the Admiralty was authorised to build and operate these fixed defences.
The plan called for coastal defence batteries at both North and South Sutor.