At the turn of the 19th and 20th centuries. The Balkans turned into a “labyrinth” of world politics, in which there was an inevitable clash of interests of the great powers, who sought to fill it with their influence. Great Britain, a world power whose global leadership began to erode by the beginning of the 20th century, was no exception. The search for the lost balance, i.e., the state of the system that would provide it with a comfortable world-political environment, determined England's attention to the transformations that were unfolding in South-Eastern Europe. Studying the Balkan policy of Great Britain allows us to reach a number of problems important for understanding the origins of the First World War: the international dimension of the erosion of the multinational Ottoman Empire and Austria-Hungary; the transformation of small countries in the region from objects into subjects of international relations; models of interaction between great powers in the process of reformatting the regional order in the Balkans. Particular attention will be paid to the mechanisms and methods of British policy in the region. The monograph is written on the basis of a wide range of different sources, some of which are introduced into scientific circulation for the first time.