How did Sage get it so wrong?

Professor Neil Ferguson struck an unusually optimistic tone this week. With just one Covid death reported on Monday, and infection levels at an eight-month low in the UK, the architect of the original lockdown said: ‘The data is very encouraging and very much in line with what we expected.’ The first half of that statement is certainly true; the second half much less so.

As an unofficial member of the government’s Scientific Advisory Group for Emergencies (he resigned in an official capacity after breaking lockdown rules) Prof Ferguson has been responsible for much of the pessimistic modelling during the pandemic. For example, his team at Imperial College were predicting as late as 30 March that only 45 per cent of the population would be protected against severe disease by 21 June, even under ‘optimistic’ assumptions. In fact, hard evidence based on the Office of National Statistics measurement shows that 68 per cent of the population already had antibodies against Covid-19 by 7 April, which meant that either they had received at least one vaccination or they had recovered from Covid-19 (or indeed both).