Many potentially effective policies are ineffective or fail due to poorly identified implementation pathways, insufficient early partnerships, and a lack of implementation and evaluation. Systems thinking and co-production with stakeholders are also necessary to deliver net zero. WS5 will collaborate with stakeholders to synthesise and apply knowledge from across the hub (WS1-4), providing crucial evidence on how to design and implement policies so that their central net zero aims are delivered, health co-benefits maximised, unintended consequences minimised and trade-offs made explicit.