In 1915 a machine christened Little Willie changed the way that wars were fought. Little Willie was a fully tracked armoured vehicle that could break a trench system. Its development was completed in December 1915, but by then it had already been superseded by an improved design, Mother. This was the first rhomboid tank, and the prototype for the Mark I which would influence a whole generation of tank building. This book details the development of the Mark I, and its surprise arrival in France in the middle of 1916 during the closing weeks of the battles of the Somme.