In November 2010, as part of a broad-ranging bilateral defence agreement, the United Kingdom and France signed a treaty providing for limited cooperation on nuclear weapons. Modest in scope, and the product in immediate terms of economic pressure, the nuclear treaty's main substantive provision is for the joint construction of radiographic-hydrodynamic facilities. 1 Beneath the surface of this treaty, however, lies a story of significant strategic shifts, and there are intriguing possibilities for future collaboration between the UK and France, and perhaps for trilateral cooperation involving the United States.The potential for UK-French collaboration spans the spectrum of nuclearweapons issues, from technology to policy, and perhaps to operational matters. These possibilities are sensitive, not only because they run into the everyday difficulties of political-military relations between the countries, but also for their relevance to two current debates: the ongoing battle over renewing the UK's fleet of strategic nuclear submarines, and international demands for multilateral nuclear disarmament.The impulse towards a nuclear partnership is not new: it existed to varying degrees over the course of the Cold War, most strongly at certain moments in the 1960s and 1970s; and in the 1990s the first steps were taken, at least towards consultation. However, for a number of strategic, political and technical reasons, no significant progress in this direction was made. By 2010, three things had changed.