BNFL have over 25 years experience of designing nuclear plant for the whole-fuel cycle. In the UK, a Nuclear Decommissioning Authority (NDA) is to be set up to ensure that Britain's nuclear legacy is cleaned up safely, securely and cost effectively. The resulting challenges and opportunities for shielding design will be substantial as the shielding design process was originally devised for the design of new plants. Although its underlying principles are equally applicable to decommissioning and remediation of old plants, there are many aspects of detailed application that need to adapt to this radically different operating environment. The paper describes both the common issues and the different challenges of shielding design at different operational phases. Sample applications will be presented of both new plant and decommissioning projects that illustrate not only the robust nature of the processes being used, but also how they lead to cost-effective solutions making a substantive and appropriate contribution to radiological protection goals.