High Quality Content by WIKIPEDIA articles! The Medium Mark A Whippet was a British tank of World War I. It was intended to complement the slower British heavy tanks by using its relative mobility and speed in exploiting any break in the enemy lines. Possibly the most successful British tank of World War I, the Whippet was responsible for more German casualties than any other British tank of the war. Whippets later took part in several of the British Army`s postwar actions, notably in Ireland and North Russia.