The metaphor of a programme of professional education as a portal or threshold to a profession is a very apt and powerful one. Professional education programmes are both the gatekeepers of a profession and its door stewards facilitating entry and initiation. The concepts and practices, or ways of thinking and acting, of a profession provide the structure and path for the passageway from novice to initiate within the profession. In this process there are a number of actors who must negotiate the portal: its dimensions; its accessibility and its boundaries. In most professions, these actors are the student professionals, the profession educators, members of the profession and often leaders within the profession. This paper aims to explore the concepts and practices encountered, developed and integrated through the portal of pre-service teacher education from these four perspectives: the student teacher, the teacher educator, the experienced teacher and the school leader. A key focus of this paper is on the operationalisation, integration and maintenance of threshold concepts of education in and through practice. Through analysis of interviews with the four groups, the aim is to explore the troublesome and transformative nature of this integration process which is at the heart of student teachers’ developing identity as teachers. In addition, the paper addresses the depth, duration and fossilisation points of the process in order to inform a greater understanding of the scope of initial teacher education within the continuum of continued professional development for teachers. This work has emerged from previous research on transformative experiences during initial teacher education which pointed at a number of threshold concepts in teaching, for example, learner empathy that seem to be part of a hidden curriculum of teacher education and not explicitly articulated in programme descriptors.