The defences consisted of three gun batteries: North Battery facing over the Rangitoto Channel, South Battery facing over the inner harbour, and Summit/Cautley Battery on the top of the hill. These first fortifications were hastily constructed, but later expanded and strengthened over 25 years by convict labor of up to 40 prisoners living in a barracks on the hilltop. The prisoners added extensive tunnel systems, underground store rooms, and various observation posts. The armaments of the fort included 64-pounder Armstrong disappearing guns, searchlights, and a remote-detonated naval minefield across the inner harbour to Bastion Point. None of the armaments were ever used in anger. A four-gun memorial saluting battery of 18-pounder World War I field guns was used, among other occasions, to salute Queen Elizabeth II on her visit in 1953.