Science and policy in extremis: the UK's initial response to COVID-19.

Drawing on the SAGE minutes and other documents, I consider the wider lessons for norms of scientific advising that can be learned from the UK's initial response to coronavirus in the period January-March 2020, when an initial strategy that planned to avoid total suppression of transmission was abruptly replaced by an aggressive suppression strategy. I introduce a distinction between "normatively light advice", in which no specific policy option is recommended, and "normatively heavy advice" that does make an explicit recommendation. I argue that, although scientific advisers should avoid normatively heavy advice in normal times in order to facilitate democratic accountability, this norm can be permissibly overridden in situations of grave emergency. SAGE's major mistake in early 2020 was not that of endorsing a particular strategy, nor that of being insufficiently precautionary, but that of relying too heavily on a specific set of "reasonable worst-case" planning assumptions. I formulate some proposals that assign a more circumscribed role to "worst-case" thinking in emergency planning. In an epilogue, I consider what the implications of my proposals would have been for the UK's response to the "second wave" of late 2020.