The majority of the literature concerning the implementation of public policy assumes that public managers can carry out new policy initiatives regardless of the behavioural, cognitive or technical demands that the introduction of such policies may make upon them. There has been a tendency to assume that managers actually have the detailed technical knowledge by which to enact such new policies. The paper proposes that in effect, public managers have to learn a range of often new and detailed techniques in order to implement what are often ambiguous policy directives. Drawing on data gathered from the introduction of capital investment appraisal in the British National Health Service, a model of Learned Implementation is presented that describes one way in which public managers can learn to enact new policy initiatives. Using a mix of six organizational processes and variables, the model demonstrates how learning occurs and is used to solve the problems that are inherent in the introduction of new policy initiatives. The model further describes how the managers routinize these solutions into job tasks and procedures and hence a policy initiative is operationalized. The paper concludes with a discussion about the difficulties of predicting the operational consequences of new policy initiatives and raises questions about knowledge, ability and capability in the implementation of public policy.