On Wednesday, Prof Neil Ferguson, a former member of the Scientific Advisory Group for Emergencies (Sage), said a lockdown one week earlier could have saved half of all lives lost to Covid-19 (Coronavirus: enforcing UK lockdown one week earlier ‘could have saved 20,000 lives’, 10 June). Later the same day at the government briefing, Prof Chris Whitty said Sage did not have enough information to make judgments in the earlier stages of the pandemic. If you are travelling on a motorway at 70 mph and you encounter thick fog, and you cannot see what’s in front of you, you don’t keep going at maximum speed on the basis that there is no evidence of an obstruction ahead. So why, given the lack of clear data, did Sage and the government not take a more precautionary approach? Why did they think we would not experience a sudden increase in infections, even as Italy was being overwhelmed? I can only surmise they thought a lack of data on infections was evidence enough that we did not have that many. This when they freely admit that in February Public Health England could only cope with carrying out testing and tracing contacts of five cases a week. It is this insouciance at the outset that has cost so many lives. Chris Counsell Morgans Vale, Wiltshire • A simple calculation of Covid-19 deaths per million of population shows that if the UK had handled the pandemic as effectively as New Zealand, we would by now have a total of just over 300 deaths, not 40,000; and we would be celebrating our full return to pre-virus normality. Mismanagement of a seriously botched industrial process, or some other disaster involving large numbers of unnecessary deaths, would result in a judicial inquiry, with those responsible facing charges up to and including manslaughter. When will such an inquiry be launched? David Simpson London • Boris Johnson says it is “premature” to assess whether his government should have imposed a lockdown sooner, which could have saved 20,000 lives. Most of us over-70s (and presumably other at risk groups) believe a review is rather urgent, as we don’t have that much time left to allow his incompetent government to wreak more havoc and for herd immunity to take its toll. Don Macdonald London • Ministers admit to a UK total of over 40,000 Covid-related deaths (the true figure may be nearer 60,000), many the result of missing PPE, inadequate testing and horrifying failures in protection of care home residents. So where are the mass street protests about this carnage, along the lines of Black Lives Matter? Don Keller Harringay, London • Join the debate – email guardian.letters@theguardian.com • Read more Guardian letters – click here to visit gu.com/letters