HMS A1 was the Royal Navy's first British-designed submarine, and their first to suffer fatal casualties. She was the lead ship of the first British s and the only one to have a single bow torpedo tube. She was actually sunk twice: first in 1904 when she became the first submarine casualty, with the loss of all hands; however, she was recovered, but sank again in 1911, this time when she was unmanned. The wreck was discovered in 1989 and was designated under the Protection of Wrecks Act in 1998. The wreck is a Protected Wreck managed by Historic England. Design and construction She was an enlarged and improved – longer than the Royal Navy's five "Holland"-type boats. Subsequent A-class boats were even larger and differed from her in several respects. Like all members of her class, she was built at Vickers, Barrow-in-Furness. She was laid down on 19 February 1902 and launched on 9 July 1902. Before she left the yard she suffered from a hydrogen explosion. Later while under tow to Portsmouth to join with the rest of the navy's submarines, seawater managed to reach her batteries, which gave off chlorine gas, forcing the evacuation of the vessel. Casualty, recovery, loss and rediscovery She was accidentally sunk in the Solent on 18 March 1904 whilst carrying out a practice attack on the protected cruiser by being struck on the starboard side of the conning tower by a mail steamer, SS Berwick Castle, which was en route from Southampton to Hamburg. She sank in only of water, but the boat flooded and the entire crew was drowned. One consequence was that all subsequent Royal Navy submarines were equipped with a watertight hatch at the bottom of the conning tower. She was raised on 18 April 1904 and repaired and re-entered service. Following a petrol explosion in August 1910, she was converted to a testbed for the Admiralty's Anti-Submarine Committee. She was lost a year later when running submerged but unmanned under automatic pilot. Although the position of her sinking was known at the time, all efforts to locate her were fruitless. It was not until 1989 that the wreck was discovered by a local fisherman at Bracklesham Bay, approximately away. It is thought that she was only partially flooded when she sank, and the resulting partial buoyancy meant that the wreck moved in the strong local currents. The wreck