Purpose: The paper aims to offer an exploration of the Banking Act 1987 which was passed following the failure of Johnson Matthey Bankers (JMB) in 1984. This Act extended the role of auditors in banking supervision by removing traditional confidentiality constraints and created a new role of "reporting accountant". The paper seeks to examine the origin and development of these new reporting roles. In addition, the paper considers the extent to which the findings of this historical investigation might contribute to current debates on the role of auditors in banking supervision. Design/methodology/approach: The paper draws on official documents, personal accounts of individuals responsible for dealing with the JMB crisis, and semi-structured interviews conducted with audit partners and banking supervisors who had direct experience of implementing the supervisory reforms instituted under the Banking Act 1987. Power's explanatory schema of controversy, closure and credibility is adopted as a framework for the analysis of documentary sources and interview data. Findings: The failure of JMB generated sufficient controversy so as to require reform of the system of banking supervision. The paper shows that JMB was a controversy since it disturbed what went before and carried with it sufficient allies for change. To achieve closure of the controversy, agreement by key actors about changes to the nature of the role of auditors was required to ensure legitimacy for the reforms. Backstage work undertaken by the auditing profession and the Bank of England provided the necessary credibility to renormalise practice around the new supervisory arrangements. Originality/value: The paper develops Power's schema which is then employed to analyse the emergence of the new role of reporting accountant and extended role for auditors in UK banking supervision. The paper provides empirical evidence on the processes of controversy, closure and credibility that help to ensure the legitimacy of accounting and auditing change.