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Limbo, or Anti Submarine Mortar Mark 10 (A/S Mk.10), was the final British development of the anti-submarine ahead-throwing weapon stemming from World War 2. Limbo was developed by the Admiralty Underwater Weapons Establishment in the 1950s. The system is a three-barreled mortar similar to the earlier Squid that it superseded. Squid suffered from a manual loading drill, which was difficult to undertake on a pitching deck in heavy seas with no protection from the elements. Limbo therefore had an automatic loading and firing sequence with all the crew under cover. It was carried on the quarterdeck of ships on a mounting stabilised for pitch and roll and was widely fitted to Royal Navy escorts from 1955 to the mid–1980s.

The range of the mortars was controlled by opening gas vents, and was between 400 and 1,000 yards (366 and 910 m). The weapon is linked to the Sonar system of the ship, firing on command when the target is in range. The rounds were projected so that they fell in a triangular pattern around the target. Limbo could fire in any direction around the ship and is reported to have been very accurate. The weapon remained in service in the Royal Navy and Commonwealth navies until the 1990s and saw active service in the Falklands War.

The firing of the Mortar Mk 10 was controlled by the type 170 sonar from the SCR (Sonar Control Room), which was generally located next to the Operations Room in the warship.

The 170 sonar was operated by 3 operators, who maintained sonar contact with the target, and effectively aimed the weapon, in bearing, range and depth. The operators were controlled by the SC (Sonar Controller) who was in charge of the SCR.

When a contact had been confirmed as a hostile submarine, the Sonar Controller manually fired the Mortar Mk 10 from the SCR upon receiving the order from the Captain in the Operations Room.

• Range: 400 to 1000 yards (366 to 910 m)
• Calibre: 12 inch
• Weight of projectile: 390 lb (177 kg)
• Mass of explosive: 94 kg minol
• Lethal radius: 5 yards (4.6 m)
• Total system weight: 35 tons including 17 salvos (51 projectiles).

• Naval Armament, Doug Richardson, 1981, Jane's Publishing, ISBN 0-531-03738-X