The Jaguar programme resulted from a successful international collaboration in all the relevant disciplines between companies having very different backgrounds in the aviation field, namely British Aircraft Corporation and Breguet Aviation (since merged with Dassault) for the airframe and Rolls-Royce and Turbomeca for the engines. It also involved collaboration in depth between government officials having different civil service structures and national practices in the two countries. Before entering into a description of the various phases of the programme and some of the problems which were met and solved it is worth briefly reflecting on the background leading to the formal start of the project in May 1965.