When was the right time to introduce lockdown measures then?
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That is a really hard question as we don't know what the government knew or the advice they had during the build up.
In the end what tipped them was the report from Imperial College (Ferguson) published on 16th March - even then Johnson came over as halfheartedly supporting it - not properly supported by the govt until the 23rd.
The study is essentially based on a basic SIR epidemiological model - that would have given the same projections in mid to late Feb - with assumptions based on the data from China. In addition data from Italy was available late Feb/early March.
Given that info and the knowledge that the testing capacity was running out and PPE stocks inadequate even for a flu epidemic - they could have locked down by Mar 10th or, preferably, introduced a series of restrictions maybe avoiding eventual full lockdown - something more like Germany or maybe even Sweden.
But I feel the fundamental problem we have here is not the exact date of the measures taken, but that the trust in government has been undermined. This was true even even before the crisis, due to 3 years of arguing over brexit.
One group (against the continuing of any lockdown) is trying, even now, to force the gov to publish the scientific evidence presented and advice it had from SAGE
I think if the government had been open, seen as trustworthy, and properly communicated with people, instead of trying to hide things, we would have acted sooner and could have emerged with a lot less spread/deaths and economic damage.
