The 2-inch mortar had been developed during the 1930s after the British Army had inspected weapons of a similar calibre in service with other European countries, including the Spanish 50mm mortar. Although deemed unsuitable for the British Army as it stood, the
Spanish mortar did serve as the starting point from which the Armament Research Department could begin development of its own version. In November
1937ten examples of the new weapon were readied with 1600 rounds each of high-explosive and smoke bombs. The resulting trials confirmed the reliability and dependability of the weapon. The Director of Artillery ordered the weapon to be placed in production in February
1938, only four months after the initial field trials, which meant that by
1939 some 500 of the weapons and their associated ammunition were already established in service as the Mk II with crews trained in the use of the weapon.