In 1926, the British War Office wanted to replace their existing Mark II tanks with a new design. In May the Royal Tank Corps Centre was asked for its opinion, which it submitted in July. One of the requirements was a weight limit of , which led to the nickname "16-tonners". Other specifications included that it could transported by rail, a sufficient supply of lubrication oil to match the range of the tank (dictated by the fuel carried), a wireless set, a gun capable of defeating enemy armour at a range of at least , fuel tanks external to the main compartments and bottom armour sufficient to withstand heavy machine-gun fire, when exposed climbing a crest. Furthermore the machine should be as silent as possible, as with previous types the engine noise tended to incapacitate the crew.