An innovative framework combining the ‘multiple streams’ (MS) and ‘punctuated equilibrium’ (PE) models of agenda-setting is used to explain the transformation of UK climate change and energy policy under the Labour Government between 2006 and 2010. The coupling of the problem, politics and policy streams by policy entrepreneurs (MS), and changes in policy image and institutional venues (PE), were critical in opening a policy window, disrupting the existing policy monopoly and enabling radical policy initiatives. The case study suggests two revisions to the models: (1) policy windows can remain open far longer than either model typically predicts; and (2) party politics, especially where party competition generates a ‘competitive consensus’, can be important for both initiating and prolonging policy change in parliamentary systems. An important factor typically overlooked by both models is the significant policy entrepreneurship role that government ministers can play, particularly when an issue becomes part of their ‘narrative identity’.