The failure to prevent tens of thousands of deaths during Britain’s brutal second wave of Covid infections was a more serious error than the timing of the first lockdown, senior scientists have told the Guardian, after a damning report by MPs on the handling of the pandemic.The scientific advisory group for emergencies (Sage) warned ministers in September 2020 that the country faced a “very large epidemic with catastrophic consequences” unless they took immediate action and imposed a “circuit breaker” to bring soaring cases under control.But the advice went unheeded and was only made public three weeks later, after Boris Johnson announced the three tier system as an alternative. It was abandoned for a national lockdown in November.Several scientists advising the government said that the failure to prevent the second wave was inexcusable given how much was then known about the virus and the imminent availability of Covid vaccines. Ministers were warned in October 2020 that the tier system was inadequate and that the death toll from the second wave would reach tens of thousands. Between Sage’s call for a September 2020 circuit breaker and March 2021, more than 80,000 people died from Covid, with the winter outbreak largely fuelled by the Alpha variant first discovered in Kent.Prof Stephen Reicher, a member of the behavioural science subgroup that feeds into Sage, said the government was “bound to make mistakes” early on in the crisis, but criticised ministers for making the same errors many times over. “To me, the real problem is the repetition of these mistakes. We made mistakes at the beginning, but then made them again and again.“Most of the time, there was a consensus among the scientists, as there was about last autumn and the need for a circuit breaker,” he added. “The real issue was not any split between scientists about what government should do, but about what scientists advised and what government did.”Reicher took issue with the MPs’ report for blaming failures, at least partially, on “groupthink”, arguing that the phrase “let people off the hook”. He said the “main problem was a paternalistic ideology” that “sees the public as a problem, that sees the private sector as the best way to run the test and trace system, and fails to see the value of public health at a local level”. He said the same ideology gave rise to the assumption – rejected by behavioural scientists – that locking down early would fail because people would become fatigued. “This paternalistic approach, where people are seen as a problem, is one of the biggest mistakes of the pandemic,” he said.Prof Peter Openshaw, a member of the government’s new and emerging respiratory virus threats advisory group (Nervtag) said that early on in Britain’s epidemic, few scientists were confident that vaccines would be developed, trialled and approved by the end of 2020. As such, many early discussions centred around when, rather than whether, people would get infected.Despite the uncertainties, scientists on Nervtag concluded that Britain needed to go into lockdown, but Openshaw said he spent weeks wondering why policymakers had not decided to take the step. “I remember feeling deeply uncomfortable about this, thinking they must have evidence that we don’t have, that has made them decide not to institute the lockdown immediately.”Speaking in a personal capacity, Prof Mark Woolhouse, a member of the modelling subgroup that feeds into Sage, said an earlier lockdown in spring 2020 would probably have saved more lives, but the number may have been far fewer than suggested at the time, and needed to be considered alongside the impact of lockdown – including deaths from disrupted health services. He said actions taken – and not taken – in January and February in the UK, internationally and especially by the World Health Organization “are likely to have been at least as important” as the decisions in March. “Hopefully, the full inquiries to come will look into that period in more detail,” he added.