This article provides insight from the Sustainable Development Unit, a top down policy, monitoring and delivery unit to support a large complex health system, the National Health Service, to embed sustainable development. The dedicated unit nurtured and supported bottom up action through top down change, it translated legal requirements, embedded good governance and engaged with stakeholders.By identifying a specific and manageable topic area the unit created an entry point to broader change and enabled action, in this case the unit started with carbon footprinting and reduction. Engagement of stakeholders was a mandate for strong governance and provided feedback of successes and future challenges. Progress was monitored through carbon reduction (18.5% over ten years), with over £1.8bn energy related savings, board approved Sustainable Development Measurement Plans (71% of trusts), and public annual sustainability reporting (85% of Clinical Commissioning Groups and trusts).