 He is best known for detailed historical studies of the institutions behind public diplomacy and for emphasizing the importance of "listening" as a pre-condition for successful public diplomacy.He coined the term reputational security for a category of enhanced security that comes to an international actor when they are well thought of by external audiences.Cull is past president of the International Association for Media and History (2004-2019), and has worked closely with the British Council's Counterpoint Think Tank.