HMS Iron Duke was the last of four central battery ironclads built for the Royal Navy in the late 1860s. Completed in 1871, the ship was briefly assigned to the Reserve Fleet as a guardship in Ireland, before she was sent out to the China Station as its flagship. Iron Duke returned four years later and resumed her duties as a guardship. She accidentally rammed and sank her sister ship, , in a heavy fog in mid-1875 and returned to the Far East in 1878. The ship ran aground twice during this deployment and returned home in 1883. After a lengthy refit, Iron Duke was assigned to the Channel Fleet in 1885 and remained there until she again became a guardship in 1890. The ship was converted into a coal hulk a decade later and continued in that role until 1906 when she was sold for scrap and broken up. Design and description The Audacious class was designed as a second-class ironclad intended for overseas service. They were long between perpendiculars and had a beam of . Iron Duke had a draught of forward and aft. The Audacious-class ships displaced and had a tonnage of 3,774 tons burthen. They had a complement of 450 officers and ratings. Iron Duke had a pair of two-cylinder, horizontal-return, connecting-rod steam engines, each driving a single propeller using steam provided by six rectangular boilers. The engines were designed to give the ships a speed of ; Iron Duke reached a speed of from during her sea trials on 2 November 1870. She carried a maximum of of coal. The Audacious class was ship-rigged with three masts and had a sail area of . Around 1871 they were re-rigged as barques with their sail area reduced to To reduce drag, the funnel was telescopic and could be lowered. Under sail alone, they could reach . The main armament of the Audacious-class ships consisted of 10 RML rifled muzzle-loading guns. Six of these were positioned on the main deck, three on each broadside, and the other four guns were mounted on the corners of the upper deck battery. The battery protruded over the sides of the ships to give the guns a certain amount of end-on fire. The shell of the nine-inch gun weighed while the gun itself weighed . It had a muzzle velocity of and was rated with the ability to penetrate of wrought-iron