Stickleback-class submarine

The Stickleback class submarines were midget submarines of the Royal Navy initially ordered as improved versions of the older XE class submarines. They were designed to allow British defences to practice defending against midget submarines since it was theorised that the Soviets had or could develop such craft.

The Royal Navy developed plans to use these craft to carry a 15 kiloton nuclear mine (based around the Red Beard weapon) codenamed Cudgel into Soviet harbours. The project was unsuccessful as there were problems finding and paying for the necessary fissile material.

Boats
There were 4 boats, launched 1954–1955:
 * X51 Stickleback, launched July 1954, sold to the Royal Swedish Navy in 1958 and was renamed Spiggen. Now on display at the Imperial War Museum Duxford.
 * X52 Shrimp, launched October 1954
 * X53 Sprat, launched 30 December 1954
 * X54 Minnow, launched 5 May 1955