In 2009, London Overground management implemented a new tactical plan for AM and PM Peak service on the North London Line (NLL). This paper documents that tactical planning intervention and evaluates its outcomes in terms of certain aspects of service delivery (the operator’s perspective on system performance) and service quality (the passenger’s perspective). Analyses of service delivery and quality, and passenger demand contribute to the development, proposal, and implementation of the new tactical plan. It is found that NLL trains were routinely delayed en route with excessive dwell time being a major cause. Near-random passenger incidence behavior suggests an even headway service may be more appropriate for NLL. The confluence of these analyses is confirmed by the corresponding excess journey time (EJT) results. Based on longitudinal analysis, evaluation shows that on-time performance increased substantially and observed journey time (OJT) decreased with the introduction of the new plan. Overall, the effects of this implementation appear to have been positive on balance. This case study thus demonstrates the applicability of automatic data generally, and certain measures and techniques in London Overground specifically, to support tactical planning of an urban railway.