As for the requirements of the new battle machine, one of the most important criteria was its off-road performance. The field of battle is difficult to traverse. It is covered in trenches, barbed wire, craters. For armoured cars, common in armies of the time, this terrain was impassable. Only tracked vehicles could deal with such obstacles.
Attempts to build such vehicles in Britain already happened, but the land forces were staunch conservatives, and constantly told inventors that they have no need for such vehicles.
Winston Churchill, at the time the First Lord of the Admiralty, displayed an interest in these new projects. Even his influence was not enough to change the army's mind. Churchill had to do it himself. In February of 1915, he created a Committee of Land Ships at the Admiralty, a small department with engineers, polticians, and naval officers. The committee was tasked with developing vehicles that would later be called tanks. The committee was headed by the head of the Naval Construction Directorate, Tennison D'Encur.
The commmitee had many projects and ideas. Mobile shields, steam-powered tractors, amazing vehicles made of two parts, connected together with a flexible chain (land ship "Pedrail"), three-tracked armoured tractor "Killen-Strait", with three wooden tracks. All of this needed to be examined and evaluated, and, if the idea was deemed worthwhile, built and tested. The finances of the committee came from the Admiralty's special treasury, which existed thanks to Churchill's timely understanding of the potential of the new weapon.
The most reasonable and promising project chosen by the committee was Ernest Dunlop Swinton's land battleship. Swinton used the American Holt tractor as a base, which turned out to be the right choice, as no other tractor measured up to the requirements for tanks.
Under the committee's patronage, Swinton successfully completed His Majesty's Land Battleship "Centipede" (also known as "Big Willy" or "Mother"). On February 2nd, 1916, at Marquis of Solsbery's estate, the vehicles was demonstrated to the cabinet of ministers, Admiralty, and General Staff. The trials were successful enough that the army agreed that these tanks need to be built. On February 8th, Big Willy was shown to King George V, who was so impressed, he shook the driver's hand. The land ship, finally and irreversibly, was given the green light.
In order to maintain secrecy, the workers assembling hulls were told they were making mobile water tanks. The name stuck, and since then, 20th century's most menacing fighting machine was called a tank. On September 15th, 1916, the tanks created panic when they arrived on the battlefield at Somme. The effect was mostly psychological, as the Mk. I tanks had neither outstanding reliability nor firepower. The first battle with tanks showed that the way out of positional war was found, and should be developed further. At that point, no one could have guessed how tanks would change the art of war.