Eventually, by the 1930s, British experiments and their strategic situation led to a tank development programme with three main types of tank: light, cruiser, and infantry. The Infantry tanks were tasked with the support of dismounted infantry. The maximum speed requirement matched the walking pace of a rifleman, and the armour on these tanks was expected to be heavy enough to provide immunity to towed anti-tank guns. Armament had to be sufficient to suppress or destroy enemy machine gun positions and bunkers. Cruiser tanks were tasked with the traditional cavalry roles of pursuit and exploitation, working relatively independently of the infantry. This led to cruiser tank designs having great speed. To achieve this they were lightly armoured, and tended to carry anti-tank armament. The light tanks were tasked with reconnaissance and constabulary-type colonial roles, with cheapness the major design factor. Vickers-Armstrong built a series of light tanks, to be sold either to the British Army who wanted to keep costs down or to foreign militaries.