From the earliest days of the UK civil nuclear programme, physical models have played a major role in supporting reactor design, development and operation. As the industry has matured, the role played by such models has changed and, despite advances in computational techniques, physical models still provide a cost-effective approach in a number of areas. Regulators still require physical evidence that processes are safe and sometimes this cannot be provided by the use of computational or analytical techniques alone. In addition, full size mock ups are employed to provide a training environment, in which teams can develop tools and techniques before site implementation. This minimises the risk of error and the received dose in radioactive areas. Consequently, physical models still play a major role in supporting safety cases for processes and operations in the nuclear industry.