HMS L24 was built by Vickers at their Barrow-in-Furness shipyard, launched on 19 February 1919. The boat was sunk with all hands following a collision with the battleship HMS Resolution during an exercise off Portland Bill in the English Channel on 10 January 1924. A memorial is located in St Ann's Church in HMNB Portsmouth on the south wall of the nave, above the most Easterly window.
HMS L24 had a length of 238 feet 7 inches (72.7 m) overall, a beam of 23 feet 6 inches (7.2 m) and a mean draft of 13 feet 3 inches (4.0 m). She displaced 914 tons on the surface and 1,089 tons submerged. The L-class submarines had a crew of 38 officers and ratings. They had a diving depth of 150 feet (45.7m) and the later variants were enlarged to accommodate 21-inch (53.3 cm) torpedoes and more fuel.
For surface running, the L-class were powered by two 12-cylinder Vickers 1,200-brake-horsepower (895 kW) diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600-horsepower (447 kW) electric motor and could reach 17 knots (20 mph) on the surface and 10.5 knots (12.1 mph) underwater. On the surface, the L-class had a range of 3,800 nautical miles (4,400 mi) at 10 knots (12 mph).
HMS L24 was armed with four 21-inch torpedo tubes in the bow and two 18-inch in broadside mounts. They carried four reload torpedoes culminating in a total of ten torpedoes. They were also armed with a 4-inch deck gun.
HMS L24 was detailed to take part in Exercise GA in January 1924, which was intended to improve submarine tactics in dealing with aircraft, both friendly and hostile. On 10th January HMS Resolution, a 29,000-ton battleship, left Portland bound for the exercise. After several hours at sea, a lookout on board the Resolution reported a slight disturbance on the surface ahead and at 11:13 a slight bump was felt.
HMS L24 was reported missing shortly afterwards and salvage vessels dispatched to the area. Unfortunately as night fell, deteriorating weather prevented any further search and by the 12th January all hope of finding survivors was lost. HMS Resolution was later checked for evidence of a collision, her chain was found to be fractured at the very bottom and this was taken as evidence of a collision. It is believed that HMS L24 was previously unaware of HMS Resolution’s position having carried out a mock attack on another ship and was surfacing when she suddenly became aware of the looming battleship. A crash dive was attempted but HMS L24 was unable to avoid the battleship.
The wreck is located at 50°22.50′N 02°37.79′W at a depth of 171 feet (52 metres). Her hydroplanes remain set to hard dive, indicating that she was attempting to take evasive action. A hatch is open and there is obvious damage where HMS Resolution sliced into her hull. The wreck is designated as a protected place.
