a simplistic analysis of the (imperfect and insufficient) data available: With caution, given the uncertainty in diagnosed cases, the epidemic appears to have grown at ~17% per day in the UK (similar to Italy 14 days before) the week before the lockdown, despite the calls for social distancing. This suggests that a lockdown was very important. It also suggests that a lockdown one week earlier could have led to an epidemic ~3 times smaller (likely translating into many thousands fewer deaths and the need for a shorter and less disruptive lockdown).

Cases offer a distorted picture due to limited testing.

https://twitter.com/imartincorena/st...96648040374272
The UK government didn't really take any action until March 12th/13th and from then on increasingly ramped up firstly weekly and then day-by-day to where we are now. The rough suggestion being that starting one week earlier could have massively improved our circumstances.