Who First Conceived the Tank?

Covered war carts were used by the Scots against the English in the mid-15th century, and Leonardo da Vinci sketched his famous "tank" design in the 1480s. Later centuries saw attempts to create wind-powered "land ships" and various steam-powered contraptions. — BBC Website

Model of Leonardo's Original Concept

Sirs, the victory in this war will belong to which of the two belligerents which will be the first to place a gun of 75[mm] on a vehicle able to be driven on all terrain. 
— Lt. Col. Jean-Baptiste Eugène Estienne, 23 August 1914

Col. Estienne

It was Mr. Churchill who, as First Lord of the Admiralty, gave the first order for eighteen tanks, or "land ships" as they were then called, on 26 March 1915. He did not inform either the War Office or the Treasury — an almost unprecedented and certainly unconstitutional reticence, dictated by fear that conventional minds might stifle a great idea. 
— Sir Winston S. Churchill, quoted in Colin Coote, ed., Maxims and Reflections, 1949

"Little Willie," First Completed Tank Prototype