This article identifies the role played by a series of medical scandals in the UK, occurring from the mid-1990s onwards, in ending a collegial model of self-regulation of the medical profession that had endured for 150 years. The state's original motive in endorsing professional self-regulation was to resolve the principal-agent problem inherent in the doctor-patient relationship. The profession, in return for its self-regulating privileges, undertook to act as a reliable guarantor for the competence and conduct of each of its members. Though sufficient to ensure that most doctors were "good", the collegial model adopted by the profession left it fatally vulnerable to the problem of "bad apples": those unwilling, incapable or indifferent to delivering on their professional commitments and who betrayed the trust of both patients and peers. Weak administrative systems in the NHS failed to compensate for the defects of the collegium in controlling these individuals. The scandals both provoked and legitimised erosion of the profession's self-regulatory power. Though its vulnerability to bad apples had been present since the founding of the 19th century profession, it was the convergence of social and political conditions at a particular historical moment that transformed the scandals into an unstoppable imperative for reform. Huge public anger, the voice permitted to a coalition of critics, shifts in social attitudes, the opportunity presented for imposing standards for accountability, and the increasing ascendancy of pro-interventionist managerialist and political agendas from the early 1990s onwards were all implicated in the response made to scandals and the shape the reforms took. Scandals need to be understood not as simple determinants of change, but as one performative element in a constellation of socially contingent forces and contexts. The new rebalancing of the "countervailing powers" has dislodged the profession as the senior partner in the regulation of doctors, but may introduce new risks. (C) 2011 Elsevier Ltd. All rights reserved.