The number of coronavirus infections in the UK soared by an estimated 1.3 million over the course of the nine days directly before lockdown, according to reports.
An investigation by the Sunday Times suggests that the Government's delay in acting may have worsened the peak of the pandemic, and is responsible for the UK suffering Europe's worst death toll.
Boris Johnson is said to have decided to bring in some form of lockdown on March 14, when new modelling shows 200,000 people were ill with the deadly bug.
But deliberations over what restrictions to bring in and when meant the PM did not ask Brits to stay at home until March 23, nine days later, by which point the modelling estimates that 1.5million people had caught the infection.