Pinchgut Island. Concern with the threat of foreign attack caused the government to review the harbour's inner defences. Barney, who had earlier reported that Sydney's defences were inadequate, recommended that the government establish a fort on Pinchgut Island to help protect Sydney Harbour from attack by foreign vessels. Fortification of the island began in 1841 but was not completed. Construction resumed in 1855 because of fear of a Russian naval attack during the Crimean War, and was completed on 14 November 1857. The newly built fort then took its current name from Sir William Thomas Denison, the Governor of New South Wales from 1855 to 1861. The fortress features a distinctive Martello tower, the only one ever built in Australia and the last one ever constructed in the British Empire. It was constructed using of sandstone from nearby Kurraba Point, Neutral Bay. The tower's walls are between thick at the base and thick at the top. However, developments in artillery rendered the fort largely obsolete by the time it was completed. The tower itself had quarters for a garrison of 24 soldiers and one officer. Fort Denison's armament included three muzzle loaders in the tower, two guns, one on a 360-degree traverse on the top of the tower and one in a bastion at the other end of the island, and twelve cannons in a battery between the base of the tower and the flanking bastion. Eventually all the guns were removed, except for the three muzzle-loading cannons in the gun room in the tower, which were installed before construction was complete. The passages within the tower are too narrow to permit these to be removed. However, from the beginning the three cannons were of limited utility. The embrasures for the cannons were too small to use the guns effectively and by the time a cannon was loaded the ship it was to fire on would have sailed past. Lastly, the guns' recoil was too powerful for the small room. In 1906, a saluting gun (pictured below) was transferred from Dawes Point to Fort Denison. In 1913 a lighthouse beacon built in Birmingham, England, and shipped to Sydney, replaced the gun on the roof of the tower. The light is called Fort Denison Light, which is still in use. In May 1942, three Japanese two-man midget-submarines attacked Sydney Harbour. When the US Navy cruiser fired on the Japanese, some of