The development of more digitalised environment is transforming the future of manufacturing. This is known as Industry 4.0. Firms do not currently fully appreciate the complex characteristics of Industry 4.0 and as a result are uncertain about what it represents for them and indeterminate as which initiatives could be beneficial to their business. In this study, an assessment model is developed to measure the level of implementation of Industry 4.0 technologies, around three dimensions „Factory of the Future‟, „People and Culture‟, „Strategy‟. The „Factory of the Future‟ is the main dimension and is composed of eight attributes: Additive Manufacturing, Cloud, Manufacturing Execution System, Internet of Things and Cyber Physical Systems, Big Data, Sensors, e-Value Chains, and Autonomous Robots. The assessment tool measures firms‟ maturity in these three key dimensions, which add up to produce an overall Industry 4.0 score. The study uses a defence manufacturing firm to develop, test and validate the model and report on 12 partners. We concluded that the focal firm has an Industry 4.0 maturity level of 59.35, above the sector average of 55.58. This research contributes to the field by empirically developing and testing a model and providing a clear analysis of major firms in the Defence supply network.