Prof Neil Ferguson, one of the Government’s leading modellers during the pandemic, has previously said the UK death toll could have been halved if lockdown had been introduced a week earlier.

But this is the first study of its kind to “formally quantify” the impact of the timing of social distancing and lockdown on the number of subsequent cases and deaths during the first wave in England, the authors said.

The natural growth of confirmed Covid cases between March 3 and June 1 was modelled, along with the hypothetical growth of cases if measures had been implemented one and two weeks earlier.

If lockdown had been implemented two weeks earlier than March 23, a 93 per cent reduction in cases would have occurred, the modelling suggested, and some 43,318 deaths “could have been avoided”.

The authors concluded: “Our simulations suggest that nearly three quarters of Pillar 1 cases (largely representing severe cases requiring hospital admission) and approximately 21,000 deaths occurring in hospitals could have been avoided by acting one week earlier; moreover, the time required in lockdown could have been halved.

“Although many factors likely contribute to the scale and severity of each Covid-19 epidemic, our modelling suggests that England’s relatively late lockdown may partly explain its comparatively high number of deaths.”

The model did not make assumptions about transmission rates, the authors added, but directly modelled the “underlying causal process” of exponential growth of cases.

They warned that the study provided an “incomplete summary” of the first wave as only pillar 1 cases – swab testing in Public Health England labs and NHS hospitals – were used, “which are far lower than the true number of infections”.

“Although our modelling is based on empirical observations and various assumptions, our results highlight the importance of acting swiftly to minimise the spread of an infectious disease when case numbers are increasing exponentially,” the authors said.