Research in this article traces the origins of a process of competitive change in British retail financial markets by looking at the emergence of cash dispensers technology, how it transformed into automated teller machines (ATMs) and how proprietary ATM networks gave way to total interoperability of cash withdrawals through a single common switch. Cash dispensers were an industry-specific innovation developed by British manufacturers (e.g. Chubb and De La Rue) which were, in turn, overtaken by US (e.g. NCR) and German (e.g. Siemens-Wincor) manufacturers. However, as the ATM became a global technology some of the leading providers (i.e. Burroughs, IBM and NCR) kept manufacturing and even their main design facilities in Scotland. The evolution of this technology illustrates changing boundaries of the banking organisation, the challenges faced by financial intermediaries to adopt on-line, real-time computing and highlights the role of network externalities in financial markets. From a business history perspective, the ATM, electronic funds transfer and other retail payment media have largely been neglected by British historians and management scholars. Yet the success of automated cash dispensers as a distribution channel in retail banking epitomises a shift in bank strategy, namely how applications of computer technology moved from being potential sources of competitive advantage to being a minimum requirement for effective competition in retail finance. This article thus promotes the idea that the history of technology must consider its users, their strategies and business models inasmuch as business histories of the late twentieth century will be incomplete without attention to developments in information and communications technologies.