The withdrawal of the United Kingdom (UK) from the European Union (EU) gave rise to its associated batch of uncertainty about the direction of this country foreign policy. With this in mind, state and non-state actors attempt to predict the role and trend of UK aid deemed the main instrument of state diplomacy. In this vein, the body of work found in the literature addresses outstandingly the nature, mission, target, significance and size of UK aid to the global south in the post-Brexit era. This paper goes beyond this prediction and establishes that the challenge for the allocation of UK aid to the global south is to balance two approaches that defray the chronicle: one is to respond to poverty-related issues, this is to say idealism approach, and the other one relates to the UK economic and strategic interests, namely, the realism approach. The combination of these two approaches is continual, UK policymakers abiding by this trend. It is then a challenge for UK aid to the global south to concur with this reality.