It’s called “flattening the peak”.  If testing can be scaled up and more people with the Coronavirus are identified; if they self-isolate; if others work from home, it may be that the Government will need to move only from the contain to the delay stage of its strategy.

It could just be that because of preparedness, or because infection and death rates are at the lower end of the expected range, the illness is contained more successfully than in Italy, and a lockdown is not needed.

However, this is unlikely.  The Government’s Chief Scientific Adviser and Chief Medical Officer seemed to indicate as much during the Prime Minister’s press conference earlier this week.  The latter, Chris Whitty, said that it’s “not just a matter of what you do but also a matter of when you do it”.

That points towards the implementation of the final stage of the strategy: mitigation, perhaps within a fortnight.  Furthermore, the number of those being tested is increasing relatively slowly (by less than a thousand a day on our count since yesterday).

As Matthew Hancock put in the Commons last week, “at that point it would be impossible to prevent widespread transmission, so the emphasis will be on caring for those who are most seriously ill, and keeping essential services running at a time when large parts of the workforce may be off sick”.

Which would presumably necessitate school closures, after all; the shutting-down of sporting and cultural events, to which Ministers are resistant, and restrictions on foreign travel: in short, a shutdown.

The central plank in the Government’s case is that timing is everything.  Mitigate too early, and people will go home; get bored; lower their guard…and re-emerge to walk slap bang into the Coronavirus as it spreads.  The peak would then be sharpened rather than flattened.

As Patrick Vallance, the Chief Scientific Adviser, indicated on Monday, the decisions that Boris Johnson and other Ministers will take about moving from delay to mitigation are guided by modelling.  Their shorthand for describing this is “the science”.

For example: “our approach is guided by the science,” the Health Secretary told the Commons on Monday.  “We are ensuring the country is prepared for the current outbreak, guided by the science at every stage,” the Prime Minister said last week.

This is true as far as it goes, and one can understand why Ministers want to cast their decisions against this clinical background.  “The science” paints a picture of objectivity, dispassionate calculation and, to borrow a word from Vote Leave, control.  The suggestion is that the vulgar business of politics can be put aside – the image that Gordon Brown and Tony Blair attempted to project when they made the Bank of England independent.

And to date, it has been, by and large.  Labour has maintained a bipartisan approach.  Only Rory Stewart has broken cover to call for an Italian-style shutdown now.

The question is whether this consensus will be maintained if we move, as expected, to the mitigation stage, at which the Coronavirus is transmitted widely.  Readers will be working out for themselves what proportion of it will catch the illness, what the death rate will be, and how that translates into absolute numbers.

We want to avoid being alarmist, and so will restrict ourselves to quoting Catherine Calderwood, the Chief Medical Officer for Scotland.  She has said that if the Coronavirus becomes an epidemic – remember: that’s very much an if – four out of five people in Scotland will catch it.  Four per cent of them might require hospital treatment.

That’s a small proportion but a large number – some 200,000 people.  It was put to the Prime Minister at that press conference this week that the equivalent in England is two million people.  There’s no way that the NHS could cope with that number.  (The latest central Government esimate for deaths appears to be 100,000.)

There’s a limit to the number of intensive care beds that can be put in place in the time available.  And to the amount of ventilation equipment.  And to the availability of those trained to use it.  The illness can also be expected to cut a swathe through NHS staff.

The knock-on possibilities for public order are too obvious to stress, and the international background is unlikely to be helpful on that score.  Prepare for early TV and social media pictures of riots abroad.

Stand back from all this, and one can appreciate why Ministers stress the role of scientific advice rather than own up to an obvious point: in the last resort, the big decisions – to move from containment to delay, and from delay to mitigation – are not scientific, but political.  They are fairly and squarely national, economic and social decisions made by the lay people that we have elected to govern us.

There will be mistakes.  And there have been.  For example, we note from our new feature “Coronavirus Count“, which restricts itself to reproducing official sources, only yesterday were those who have arrived from Italy advised to stay indoors and avoid contact with other people.  The advice from 111 to people returning from Italy lagged behind changes announced by Public Health England.

More errors will follow.  The wheels of the state may grind exceeding small, but they grind slowly.  In any event, it is far from clear that it has the capacity to move quickly enough.  Italy’s severe restrictions appear to have been slapped down after the illness was already in circulation.

But by and large, Boris Johnson’s regular press conferences with the Chief Scientific Adviser and Chief Medical Officer have been fact-based, open, and “transparent”, as the jargon goes.  The Prime Minister has never specialised in radiating panic and isn’t going to start now.  To date, nearly 26,000 people have been tested.

None of which will blunt the sharp edges of the choice that the Prime Minister may have to make sooner rather than later.  One way of thinking about it – not that he or anyone else would put it this way – is that Ministers must trade off a rising number of deaths against a decline in economic activity.  The Treasury interest is in avoiding mitgation for as long as possible.  The Department of Health interest is to move to it as soon as is necessary, and not a moment later.

This decision cannot be palmed off to, say, Public Health England, or more broadly to “the science”.  As the old saying doesn’t quite put it, scientists advise but Ministers decide.  The model that Johnson is looking at cannot itself take decisions.  The Chief Medical Officer is not the Prime Minister.  The buck stops not in a laboratory test-tube, but on Johnson’s desk.