ABSTRACT Between the 1935–1936 Abyssinian crisis and the 1938 Munich conference, Britain’s interests in the Balkans and its relationship with other Great Powers limited British policy towards Yugoslavia. This analysis points to a higher level of British influence in Belgrade in the mid-1930s than is usually recognised in the historiography and argues that by not responding adequately to security challenges in the Balkans after the withdrawal of French influence from the region, Britain contributed to a power-vacuum for Germany to fill. As the British position in Southeastern Europe weakened after summer 1936 due to advancing Italian and German penetration, Yugoslavia’s importance grew in the eyes of Foreign Office officials. However, Britain’s position in Belgrade eroded to such a degree by late 1938 that Yugoslavia was no longer willing or able to offer any assistance in the event of war. This examination provides a better understanding of Britain’s interests in Southeastern Europe by highlighting the geo-strategic importance of Yugoslavia and the Balkans as a buffer zone to Central Europe and a flank of Britain’s Mediterranean routes when the balance of power in the continent was disturbed to British disadvantage.