The engineer Lieutenant Walter Wilson and the industrialist Sir William Tritton had cooperated in 1915 to develop the Mark I, the world's first operational tank.

Major Philip Johnson of Central Tank Workshops was impressed when he was shown a wooden mock-up during a visit to Britain late 1917.

It seems that early in the design process Wilson considered building an alternative or parallel Male version fitted with a 2-pounder (~40 mm gun) in the superstructure but he had abandoned these plans by March 1918.

The design by Wilson had elements of both the Mark I and the Whippet: a similar but smaller tracked rhomboid chassis of the former and fixed turret like the latter.

A novel feature was the separate compartment in the back, housing the 100 hp (75 kW) engine (a four-cylinder shortened Ricardo design) and behind it the epicyclic transmission.

A production of 450 vehicles had been ordered even before the prototype was finished and this number was now increased to 700, to be manufactured at North British Locomotive in Glasgow and later at Metropolitan, Coventry Ordnance Works and the Patent Shaft and Axletree Company.