The ironclad battleship HMS Audacious was the nameship of an experimental class of armoured battleships designed to expand on the success of HMS Warrior built ten years before. The ships were intended to act as the frontline of the modern battlefleet, but being such a recent innovation, they were fraught with difficulties.
Audacious was built at the Napier shipyards and cost £246,482 to complete. She was launched in February 1869, and by September 1870 was ready for active service. She did not actually fire her guns in anger during her lengthy service life, which continued after her removal from frontline duties in 1902, by which time she was very obsolete. Upon her conversion to a training ship in 1904 she was renamed Fisgard (after the French translation of the Welsh town Fishguard), and fulfilled this capacity until her further redesignation as a repair ship named Imperieuse in 1914, in which form she continued for another 13 years.