With a voice in London once again banging the "herd immunity" drum, the time has come for Nicola Sturgeon to follow Jacinda Ardern by loudly saying "no way, not EVER"

It's going to be a source of bafflement and embarrassment to SNP members for many years to come that the Scottish Government remained in lockstep with London during the period when Vallance and Whitty were quite openly planning to achieve 'herd immunity' by deliberately allowing 60%+ of the population to be infected - a crazy and immoral strategy that would have cost hundreds of thousands of UK lives, that wasn't seriously contemplated by more than a tiny handful of other countries, and that is considered so extreme that even Donald Trump eventually disavowed it. The charitable interpretation is that Nicola Sturgeon and her colleagues were only hearing the UK government's version of "the science" and therefore didn't realise how much of an outlier it was in international terms, how sharply it diverged from World Health Organization guidance, and how catastrophic the loss of human life would have been.

But there are no such excuses anymore. Anyone who has been paying attention over the last few weeks knows the score. So now that the UK government's "chief pandemic modeller" is suggesting that the lockdown should be lifted and that we should go back to allowing most of the population to be infected and put at risk of severe illness and death, we really do need Nicola Sturgeon to immediately knock this one politely and firmly on the head. We need to hear her echoing the words of Jacinda Ardern by saying that 'herd immunity' will never be acceptable to her or to any other Scot, and that the "Four Nations" approach will be immediately abandoned if London start flirting with it again.

The 'chief modeller' in question is not from the Imperial College team, incidentally - he's Graham Medley, the head of another team from the London School of Hygiene and Tropical Medicine who also advise the government. The language he uses is deeply disturbing - he effectively implies that the old should be sacrificed for the best interests of the young, which suggests that he knows full well that a biblical death toll would be unavoidable if he gets his wish. But of course the whole notion of generational sacrifice is bogus anyway, because we've seen large numbers of young people become seriously ill and dying. The two nurses that were mourned today were both in their thirties. The carnage that Medley wants to unleash would be no respecter of youth.

He suggests that people should be infected in the least deadly way possible - as if there's some kind of 'non-deadly' way to catch a virus with a death rate estimated as being as high as 1.4%. He rubbishes the idea that mass-testing might form the basis of an alternative exit strategy, simply because his mathematical modelling suggests that the virus will start spreading again as soon as lockdown is lifted - but that takes us straight back to the idiotic error that got us into this mess in the first place. During the early weeks of this year, the government were totally ignoring the real world experience in China and South Korea and were putting all their eggs in the basket of mathematical modelling instead. That led them to make two huge false assumptions - a) that the virus was much less deadly than it actually was, and b) that it was less controllable by means of testing and tracing than it actually was. South Korea has clearly demonstrated that the number of new cases can be kept persistently low by that method. It would be crazy to condemn hundreds of thousands to death without at least attempting that ourselves.

The message to the Scottish Government must be: don't even think about ending lockdown until there is a credible exit strategy in place that does not involve sitting back and allowing the majority of the population to be infected. Testing and tracing would inevitably be central to any such strategy.