The Light Tank Mk VII ( A17 ) , also known as the Tetrarch , was a British light tank produced by Vickers @-@ Armstrongs in the late 1930s and deployed during the World War II . The Tetrarch was originally designed as the latest in the line of light tanks built by the company for the British Army . It improved upon its predecessor , the Mk VIB Light Tank , by introducing the extra firepower of a 2 @-@ pounder gun . The War Office ordered 70 tanks , an order that eventually increased to 220 . Production was delayed by several factors , and as a consequence , only 100 to 177 of the tanks were produced .