Hugh Hale Leigh Bellot (1860–1928) was a key figure in the process of the transformation of international law in general and international criminal law in particular generated in the context of World War I. This chapter looks at the biography and the intellectual work of a man, who, being a Doctor of Civil Law called to the bar in 1890, in 1915 became a founding member and honorary secretary to the Grotius Society. The aim of this society was to promote impartial discussion on the Laws of War and Peace, and on their reform as a consequence of what those involved considered to be the “new conditions” in World War I. For the time after the war this chapter discusses the crucial contribution of Bellot in the discussions within the International Law Association on the creation of an international criminal court. In general the chapter aims to put Bellot’s contribution into a context that looks at the same time into the nineteenth as well as the early twentieth century and thereby clarifies the position of this important man at the crossroads of international criminal law