Much attention has been paid to the processes through which students in medical schools acquire knowledge, skills and values and form professional identities that establish new ways of thinking and relating as doctors. Yet there has been little exploration of the influence of the specific organisational culture of different medical schools with different histories, behaviours and practices. In London, the Todd Report (1968) marked the beginning of a process of successive mergers and a strengthening of ties with multi-faculty colleges to ensure medical students engaged with a broader academic setting and had close access to the sciences. This paper uses the merger between Guy’s and St Thomas’ which created the United Medical and Dental Schools (UMDS) in 1982, and the later merger between UMDS and King’s College in 1998 to explore the nature of institutional identity in medical students and the ways in which it was made and remade over the period. Drawing on a wide range of sources from student memoirs to interviews with medical school staff and students, it analyses how a variety of social formal (teaching) and informal (sport) interactions between students and teaching staff created and embedded strong and emotional attachments to a particular medical school. Being a ‘Tommy’s’ student was not the same as being a ‘Guy’s’ student, particularly on the rugger pitch. It suggests that the early merger had less of an impact upon students because the pedagogic model and teaching structures remained the same; this enabled identity to be preserved through the allegiances to teaching hospitals. The later merger was a more complex organisational reconfiguration which produced a much larger intake of students who were then required to move between different clinical sites. This limited the opportunities to form strong attachments to specific sites. During the same period, the pedagogic model changed and other factors such as the European Working Time Directive forced new ways of working which meant that identity began to shift from specific institutions to student cohorts.