The first vehicle was nicknamed "Little Willie" (weighing 14 tonnes) and motored on 8 September 1915, and a new design became the Mark I tank. The name 'tank' was the term chosen by December 1915 for this new weapon as it resembled a steel water tank, and of course as a cover, and not 'Landship', as the Navy had proposed after a group was formed by Churchill in February 1915, known as the "Landship Committee" to oversee development by the Navy and then jointly by the Navy and Army. A final specification was given late September - known as "Big Willie", later "Mother" (weighing 30 tonnes). "Little and "Big Willie" underwent trials at Hatfield Park on 29 January and 2 February 1916 on the invitation of the Marquis of Salisbury, and obstacle groundwork was undertaken by 3rd (Mid Herts) Battalion - clearly illustrating the importance of Hertfordshire in the tank's history.

On 12 February 1916, an order was placed for 100 "mother" types - later 150. The first Tank Training Centre was established at Thetford. By 30 August, the first 50 tanks had been delivered to France - either 'male' or 'female'. The former had two 6-pounder cannons and six Hotchkiss machine guns and the other one had four Vickers MGs, and one Hotchkiss - both with 8 crew members. The first use of tanks on a battlefield was at the Battle of Flers-Courcelette on 15 September with only 32 tanks engaged - many broke down but around 10 burst through the German Lines. Unfortunately, the attack was not followed up (they had been rushed into combat too early, despite Churchill's and others' wishes, but had proved their value as capable of crossing trenches or craters (9 ft across) and driving through barbed wire for infantry to follow). After the 1916 Battle of the Somme, Field Marshall Douglas Haig ordered 1,000 Mk IV and Mk V tanks. At the Battle of Cambrai in September 1917, the Tank Corps made an unprecedented breakthrough, but here again it was not fully followed up, relying in this case on the Cavalry!

Many of the 'Presentation Tanks' brought back from Flanders to raise money for bereaved families and injured troops were erroneously described in some instances as German tanks, having their black iron cross painted on the sides - however, these were recovered British tanks that had been captured or recovered after breaking down (the German Army had some 50 in use by the time of the Armistice).

German forces using captured British Mark IVs	Mark IVs near Cambrai, likely after suffering mechanical failure.	Mark IV destroyed by the Germans on the Western Front in 1917
German captured Mark IV in 1917	A destroyed Mark IV	Germans testing a Mark IV by using it to destroy a tree

Tanks in the Great War