This thesis investigates the day-to-day practice of Renaissance diplomacy through a case-study of Gregorio Casali, one of a number of Italians in the Roman diplomatic corps who served foreign princes, in Casali's case King Henry VIII of England. It outlines and analyses the key elements of the resident ambassador's role, shifting the focus of study from the traditional emphasis on official negotiations and such formal sites for the exercise of power to consider too informal relationships and arenas for diplomacy. Chapters consider the diplomat's role in Rome (the most developed diplomatic centre of its day); the relevance of family and friendship networks in Casali's career; the importance of hospitality and liberality in diplomatic life; giftgiving and 'bribery'. Drawing on recent scholarship relating to such issues as the house, household and gift-giving, the thesis situates Renaissance diplomacy in its broader social context. It thus contributes to the new trend among historians of diplomacy to adopt methods from social and cultural history, but, in applying the methodology of microhistory, takes this to a new level. As well as raising new questions about the role of the resident ambassador and his interaction with other diplomatic and political actors, the case of Casali and his family draws attention to the important issue of the employment of foreigners in diplomatic service during this period, allowing a consideration of how loyalty was understood and allegiances were managed. The thesis argues that the literature to date has failed to acknowledge the variety of advantages that such men afforded to their employers. In identifying some key patterns of diplomatic practice during these years, this study aims to contribute some benchmarks against which historians can in future assess particular diplomatic missions, variations in the practice of different countries and changes in the structure and practice of diplomacy over time.