Orders for the Mk I and Mk II Cruiser tanks were limited because the British army had decided to produce a more advanced and faster cruiser tank with Christie suspension (J. Walter Christie) and have better armour. In 1936, General Giffard LeQuesne Martel, a pioneer in tank design, who had published works on armoured warfare and pioneered the lightly armoured "tankette" to enhance infantry mobility, became Assistant Director of Mechanization at the War Office. Later that year, Martel witnessed demonstrations of Soviet tank designs, including the BT tank, which had been influenced by Christie's work.He urged the adoption of a tank that would use the suspension and follow the Christie practice of using a lightweight aircraft engine, such as the Liberty Engine. The government authorized the purchase and licensing of a Christie design via the Nuffield Organization, rather than contact the Soviet authorities.
The vehicle obtained from Christie became the basis of the Cruiser Mk III (A13). It had to be extensively redesigned by Morris Commercial Cars as it was too small and had several faults that Christie had not addressed.A new company Nuffield Mechanization & Aero Limited was formed for the development and production of the design.
At a meeting of the General Staff, an official specification was determined, which included 30 mm (1.2 in) armour, a 2-pounder gun and a road speed of 30 miles per hour (48 km/h). A subsequent review of the specification by Martel and Percy Hobart approved 30 mm armour all round provided cross-country speed could be kept at 25 miles per hour (40 km/h). Pending the delivery of the A13, an interim design was approved from the A7, A9 and A10, the A9 being selected.
The first prototype (A13-E1) was delivered in 1937. Following the testing of two prototypes, the A13 was ordered into production. The original order was for 50 tanks and 65 had been built by mid 1939. The Mk III weighed 14 long tons (14 t), had a crew of four, a 340 horsepower (250 kW) engine and a top speed of 30 miles per hour (48 km/h) and was armed with a 2 pounder gun and a machine-gun. When it was introduced into service in 1937, the army still lacked a formal tank division.