Background: A major gap in environmental policy making is learning lessons from past interventions and in integrating the lessons from evaluations that have been undertaken. Institutional memory of such evaluations often resides externally to government, in evaluation practitioner contractors who undertake commissioned evaluations on behalf of government departments.

Purpose: The aims were to learn the lessons from past policy evaluations, understand the barriers and enablers to successful evaluations, to explore the value of different types of approaches and methods used for evaluating complexity, and how evaluations were used in practice.

Setting: A meta-evaluation of 23 environmental evaluations undertaken by Collingwood Environmental Planning Ltd (CEP), London, UK was undertaken by CEP staff under the auspices of CECAN (the Centre for Evaluation of Complexity Across the Nexus – a UK Research Councils funded centre, coordinated by the University of Surrey, UK). The research covered water, environment and climate change nexus issues, including evaluations of flood risk, biodiversity, landscape, land use, climate change, catchment management, community resilience, bioenergy, and European Union (EU) Directives.