In the mid-1940s, British scientists were divided by debates about the role, meaning and management of the sciences as they transitioned from war to an uncertain peace. In pursuing its own project of post-war institutional renewal, the Royal Society – Britain’s elite scientific academy – was intensively involved in these discussions over the organisation, conduct and governance of science. Through a survey of its activities in the period 1945-55, this chapter demonstrates a deep ambivalence within the Royal Society itself about its identity and purpose, its relationship to government, and the aims and values of science in the post-war polity. Against a self-generated historiography which emphasised continuity of tradition and unity of purpose, the Royal Society was an ideologically fractured organisation whose formal role in the governance of British science was heavily contested. Nevertheless, pervasive informal and bureaucratic links with departments of state allowed the Society to exert soft power – or influence without responsibility.