This study seeks to explain major shifts in health policy and focuses on the politics of hospital mergers. It takes as case studies two governmentally-led hospital mergers in the 1990s - one in London and one in Reykjavik - when national governments, as part of broader administrative reforms, decided to merge teaching hospitals in their capitals. The decision to merge, and the implementation of the decision, followed a long history in both cities, in which the mergers had been repeatedly held up as highly desirable but had always been blocked or abandoned. The merger decisions in the 1990s represent the impossible becoming possible and stand out as defining moments for the way they shape the successive course of events in their respective health care systems.