The referendum was the defining issue of 2016. We convened a group of experts to clarify what was at stake for the UK’s environment. It produced impartial and salient knowledge, and worked closely with stakeholders to feed it into very fast moving policy processes. Its work underpinned NGO campaigns, culminating in the PM’s decision to campaign directly for environmental voters, and informed the work of Parliament. The very strength of the resulting evidence base is arguably why the environment was not more heavily contested during the referendum. The project is now directly informing the choices around the delivery of Brexit.