The Armistice ended the war in 1918 and it would never be tested in combat but development continued for the post-war needs of the British Army.

The unusual suspension proved problematic and the earlier tanks were replaced by a Vickers design - the Medium Mark I - in the 1920s.

[2] Major Johnson, working at the Mechanical Warfare Department's grounds at Dollis Hill, identified that a more powerful engine and a sprung suspension would be needed.

[3] Before the war a wooden mockup of the Mark D had been built and shown to members of the Tank Corps and an orders for ten prototypes placed (four from Fowler and six from Vickers).

[5] Sufficient funds were provided for production of 45 tanks complete with Rolls-Royce engines, later cut to 20 of which only three were built - by the Royal Ordnance Factory - based on the D** and known as the "D Modified" (DM).