Science proceeds through challenge and disputation, and new theories are tested unflinchingly against evidence. Yet Ministers and other advisers reported that they felt it difficult to challenge the views of their official scientific advisers. Those in Government have a duty to question and probe the assumptions behind any scientific advice given, particularly in a national emergency, but there is little evidence sufficient challenge took place. However, even when UK policy had changed to bring in a comprehensive national lockdown, the role of non-pharmaceutical interventions against covid-19 was complex, inconsistent and opaque for most of the rest of 2020.