During the Cold War, the escalating costs of the design and development of new military weapons technologies prompted European governments to look to cooperative armaments programmes as a means of sustaining and enhancing European military technological capabilities. Whilst the failure of some of these armaments cooperation initiatives at the negotiation stage has been noted in passing (see for instance, Matthews, 1992; Bitzinger, 1994) there has been little or no discussion of the nature of the negotiation process between governments on armaments cooperation programmes, nor any discussion as to why negotiations have succeeded or failed. Our paper will provide a case study of the challenges of creating the conditions for knowledge-making and knowledge-use in such programmes by examining the Anglo-French Variable Geometry (AFVG) military aircraft programme and the causes of French withdrawal from that programme in 1967. Uniquely, this paper will draw on material from French diplomatic and corporate archives (in particular those of the French aircraft company Dassault) in addition to UK government and corporate archives to explore the reasons behind the collapse of the negotiations. The paper illustrates the balance that sovereign nations have to strike between defending their own interests in joint projects and seeking mutual benefit from them. Our account contributes to debates about the nature of government-to-government negotiations by emphasising the impact of power asymmetries between the French and the British, the role of parallel Government agreements with domestic (primarily French industrial) interests and the escalating commitment of the British to what many observers saw as a failing course of action.