What determines the feasibility of a project?

The history of complex computer-based projects throughout the world is not glorious. The recurring pattern is at best late delivery, inadequate facilities and grudging acceptance. Frequently the problems are found to be so severe that the project is abandoned at a late stage, after significant effort has been wasted. The official (MoD) policy of progressive risk reduction by concept formulation, feasibility studies, project definition, full development_{and production before the system goes in service is evidently not giving attention to the problems that arise in practice. The paper analyses the situation and suggests how to improve it}