This third Unit provides a systemic approach to managing complex projects, using nuclear decommissioning as a case study. It begins with project planning, which defines outputs, tasks, phases and performance indicators. Then, it explores project organising, focusing on roles, responsibilities and stakeholder governance. To manage complexity, the unit introduces the concept of a programme of projects, which decomposes large-scale efforts into manageable sub-projects. Since these projects face both structural and dynamic uncertainties, strategies must be adapted to their level of unpredictability—ranging from traditional planning to agile learning. The final part applies these principles to nuclear decommissioning, highlighting the tension between safety and efficiency, and the critical challenges posed by radioactive waste management.