SIR – Science proceeds by putting forward conjectures or hypotheses, collecting empirical data to test them, and accepting, rejecting or modifying them on that basis.

The implication is that our scientific understanding is not fixed, but changes as evidence accumulates. In the United Kingdom the initial decision to impose lockdown to control the effects of Covid-19 was based on a conjecture or model that has now been tested against real data and is found to be wanting.

The model predicts that, under the sustainable public health measures taken by Sweden and in the absence of lockdown, there should now be 60,000 deaths in that country from Covid-19, whereas there are currently only about 3,000 there, with deaths now well past the peak and declining….