Theories of international norm diffusion rely on accounts of entrepreneurial action almost exclusively identified as normative non-state actors who persuade powerful states to change their behaviour. We argue that powerful state agents can (also) be moral norm entrepreneurs and explicate the foreign policy acts that make them significant agents of international socialisation. Unlike non-state actors who set the agenda by advocating for new norms, foreign policy leaders leverage their identity and position to advance the recognition and diffusion of already established norms by reframing the moral prerogative of the ‘national interest’. The paper examines a prominent case, namely former British foreign secretary, Mr. William Hague's promotion, through the offices of the British Foreign Commonwealth, of the international norm prohibiting use of sexual violence in conflict. We ask why and how did the United Kingdom and William Hague devote the attention and resources of the foreign policy apparatus to further this norm established more than a decade earlier in the Rome Statute of the ICC and by gender justice advocates? Crucially, our findings highlight the role of foreign policy leadership in re-framing conflict-related sexual violence as a threat to national and international peace and security, the strategic use of the individual positioning of the foreign minister, the harnessing of the foreign policy machinery to mobilize commitments from other states through networked diplomacy, and seizing international political opportunities to promote the take-up of the norm.