This paper presents an exploratory case study to examine information systems development (ISD) processes in a low maturity environment, and to understand the role of control mechanisms in project success. The case involves the development of a large scale bank information system, which progressed without a fully-defined "master plan" or much reliance on formal development methodologies, but was successfully launched nevertheless despite some delay. Data were analyzed from the lens of control modes. Results show that clan control emerged as a dominant form of informal control in a high complexity and low methodological maturity environment, and end-to-end user participation through collocation with the developers served as effective outcome control, which appeared to be a critical success factor. The reliance on behavior control was marginal, although the project manager's effective leadership as a form of self-control also played a role in project success. This work contributes to ISD research in general and the development of a control perspective to user participation in ISD. One of the practical implications is that potential problems associated with the absence of formal methods in a low ISD maturity environment may be overcome by strong user control over the process and quality via extensive participation.