This paper compares two major exhibitions of Dutch and Belgian art held in London’s Royal Academy of Art in the 1920s. Part of a new strategy of public diplomacy, both ventures owed much to the initiative of binational friendship associations who, aware of Britain’s importance in diplomatic and commercial terms, saw in displays of their respective artistic heritage a means of projecting their image to a wider but also elite British public. Ironically, the rivalry between these organisations led to an expansion of the scale and scope of their exhibitions that, apart from setting the tone for many similar enterprises to come, necessitated and facilitated increasing international collaboration. Apart from analysing the function of art as ‘cultural capital’ in Dutch and Belgian cultural diplomacy of this time, which was even more complicated by both countries’ joint origins (what counts as ‘Dutch’, what as ‘Belgian’, the further back you go in Low Countries history?), the paper consequently also investigates the ways in which this cultural-diplomatic competition contributed to the development of interwar internationalism.