The present paper analyses the production of knowledge pertaining to British state visits in the twentieth century. It first highlights various uncertainties in relation to state visits that the various actors in the Foreign Office and the Palace experienced historically. Second, the chapter discusses how knowledge production has changed over time. It presents a long-term perspective and argues that two distinct phases mark this change. During the first phase from the beginning of the century up until the 1960s, knowledge about state visits was developed reactively, in response to specific situations, which is referred to as practices of actualising knowledge. The second phase, from the 1960s onwards, was characterised by targeted interventions made with the deliberate intention of making more knowledge available and to develop general ideas and standards. This procedure is referred to as systemizing knowledge.