This article asks whether the UK's defence technology base is a potential solution to industrial underachievement or whether it is perhaps at the heart of the problem. In the UK, firms seem often to have opted for defence as the best route to business success. This is often portrayed as the result of short-sighted management, but it is perhaps more analytically useful to consider the ways in which this comes about. Drawing on a wide range of sources, we focus on the production history of Vickers/VSEL at Barrow in Furness, Cumbria. Once a highly diverse engineering company, VSEL became almost entirely synonymous with shipbuilding, and the building of the Trident submarines. This level of defence dependence came about following a process of active marginalisation of non-defence work which created a monoculture within the company for the first time and in which the perceived status of civil engineering declined in relation to 'superior' defence requirements. The identification of the company's interests solely with the Trident programme required a period in which employment was driven up to unsustainable levels, followed by sharp reductions in, and impoverishment of, the skill mix in a previously diverse workforce.