Between 20,000 and 30,000 lives could have been saved if the UK had locked down a week earlier, a leading adviser said, as he told how scientists grew increasingly concerned about the lack of a clear plan.
Professor Neil Ferguson, from Imperial College London, whose modelling was instrumental in persuading the Government to bring in the first lockdown, suggested there was a growing realisation in early March 2020 that the country was heading for a large number of deaths.
It came after Prime Minister Boris Johnson's former top aide, Dominic Cummings, told MPs that mistakes meant "tens of thousands of people died, who didn't need to die".
Asked on BBC Radio 4's Today programme at what point the Scientific Advisory Group for Emergencies (Sage) determined that a policy of pursuing herd immunity would lead to a vast number of deaths, Prof Ferguson said a key meeting was held at Imperial with the NHS and the London School of Hygiene and Tropical Medicine on March 1 "which finalised estimates around health impacts, so the week after that really".
He said he "wasn't privy to what officials were thinking within Government", but added: "I would say from the scientific side there was increasing concern in the week leading up to the 13th of March about the lack of clear, let's say, a resolved plan of what would happen in the next few days in terms of implementing social distancing."
Prof Ferguson was also asked how influential Sage was in changing the policy from one of herd immunity to one of lockdown.
He said: "I think the key issue... it's multiple factors, partly the modelling, which had been around for a couple of weeks but became firmer, particularly as we saw data coming in from the UK, and, unfortunately, I think one of the biggest lessons to learn in such circumstances is we really need good surveillance within the country at a much earlier point than we actually had it back in March last year.
"As we saw the data build up, and it was matching the modelling, even worse than the modelling, let's say it focused minds within the Government."
He said locking down a week earlier would have saved "20,000 to 30,000 lives" adding: "I think that's unarguable."
He said: "I mean the epidemic was doubling every three to four days in weeks 13th to 23rd of March, and so, had we moved the interventions back a week, we would have curtailed that and saved many lives."
On the forthcoming June 21 road map date for England to lift all legal limits on social contact, Prof Ferguson said it hangs in the balance.
He said experts are still concerned about issues such as the transmissibility of the Indian variant, and "Step 4 (of the road map) is rather in the balance, the data collected in the next two to three weeks will be critical".
He added: "The key issue as to whether we can go forward is will the surge caused by the Indian variant - and we do think there will be a surge - be more than has been already planned in to the relaxation measures?
"So it was always expected that relaxation would lead to a surge in infections and to some extent a small third wave of transmission - that's inevitable if you allow contact rates in population to go up, even despite immunity - but we can't cope with that being too large.
"In the next two or three weeks we will be able to come to a firm assessment of whether it's possible to go forward."
