This thesis outlines a study into institutional change analysing how certain senior individuals, called opinion leaders, were able to achieve change within the strongly institutionalized environment of medical education. It is situated in the complex and contested context of the English National Health Service, which for more than 60 years has seen numerous managerial, organizational, political and professional changes, which have impacted upon the roles and relationships of medical professionals, managers and government.Adopting a retrospective case study approach, the research centres on the specific case of the Enhancing Engagement in Medical Leadership (EEML) project, which had national-level sponsorship and status, directly involving a multitude of senior NHS bodies, representatives and individuals, to embed leadership and management training into medical curricula. Medical curricula are a mediated result of cultural, social, political and economic forces (Kuper and D'Eon, 2011) rooted in the construction of professional identity and transformation from lay person to professional. Prior to this project, there had been limited attempts to engage the medical profession in leadership and management conspicuously through the curriculum, because of the difficulty of including new content into already crowded specialty curricula, given the constraints of time and resources for medical training.Using conceptual insights into agency in institutional theory, such as institutional work (Lawrence and Suddaby, 2006) and institutional entrepreneurship (DiMaggio, 1988); practice theory (Feldman and Orlikowski, 2011; Nicolini, 2012); social position (Battilana, 2011) and capital (Lockett et al., 2014; Bourdieu, 1986), this study explores how project members enacted change within medical education. It analyses the processes involved in their actions and practices and establishes how this case furthers understanding of strongly institutionalized environments. Interviews were conducted with members of the EEML project team and steering group, many of whom had positions of influence and status in other relevant organizations in this field. In addition, a review of documentary data encompassing published and non-published project materials was undertaken. An open coding and thematic analysis approach was taken to gain deeper insight into the interview data, whilst the documentary evidence was used to confirm and support the interview analysis.This case study research reveals that contextual and environmental conditions, as well as exogenous shocks and endogenous motivation led to this change initiative occurring. Routine and recognised 'practices' resulted in significant change through embedding the Medical Leadership Competency Framework (MLCF) into contested medical curricula space. Opinion leaders were able, with other project members, to adopt an approach to change, understanding the prevailing conditions, identifying the project's purpose and committing to an emerging form of practice known as 'mirroring'. Moreover, this study explores how opinion leaders achieved change through making use of theirs' and others' capital resources to form a cross-field collective capital, known as system capital. Using this, they adopted a disposition in their practice beyond professions known as system centrism.