The prospect of nearly 1,000 troops emerging from their barracks and on to the streets of Britain will be a shock to the system. Other countries may be used to the sight of soldiers outside palaces and parliaments, at stations or large venues, but not Britain. This, remember, is a country that prides itself on the fact that most of its police are armed with nothing more than a stick.

France has got used to soldiers outside Paris museums, or on patrol through even the quietest rural village – the sight normalised after a state of emergency imposed in the wake of the terrorist attacks in November 2015 and in place ever since. Those with long memories in Northern Ireland recall only too well when a military presence formed part of the landscape. But for the rest of the UK, it will be a strange novelty.

Will people find it frightening – or reassuring? When the army rode to the rescue to guard the London Olympics in 2012, after a private security firm fell short, the public embraced them. Soldiers were greeted warmly by visitors glad to know they were there.

But the context was different then. The military were being deployed against the abstract possibility of an attack, not in the immediate aftermath of a horrifically real one. This time, the sight of soldiers – and the current plan allows for up to 3,800 of them – on the streets follows a bombing whose cruelty has barely begun to sink in. The military presence will be a reminder in human form that the terrorist threat level has been raised from severe to critical for the first time in a decade. There is some ambiguity over whether that means the security services believe another attack is likely or simply possible, but either way it is chilling.

And there is another factor about the timing that cannot be ducked. Troops are being deployed in the middle of a general election campaign. That is new and unsettling terrain for British democracy.

Inevitably, it has prompted some to be sceptical, codedly accusing Theresa May of opportunistically ramping up the threat level and the state of public anxiety, all the better to project her as the safe and prime ministerial pair of hands the country needs in fraught times. Others insist that these are purely operational decisions taken by security chiefs with no thought to politics. (Meanwhile one former senior police officer suggests to me that the truth might lie in between: with key officials, including those who’ve worked closely with May in the past, taking operational decisions they know will find favour with their political masters. Or as he put it: “They know which side their bread is buttered.”)

Still, you don’t have to detect any questionable motives, still less a conspiracy, to worry about this development and hope it won’t last long. Past precedent suggests that these “critical” periods last just a few days, as the security services catch and “roll up” terrorist cells and networks. For that reason alone, we must hope that this critical state ends quickly.

But there is a less concrete reason too. No one wants this heightened martial state to last so long that we get used to it, that it becomes normalised, as perhaps it has in France. To be specific, we have to hope there are no troops on the streets of the UK on 8 June. That would feel like an election under siege.

Such a notion is to be rejected for the obvious reason that it’s not true. The horror that was unleashed in Manchester is of a depth that is proving hard to fathom: the deliberate slaughter of children has pierced even those who thought they were becoming inured to the nihilism of these killers. But it has not besieged our democracy; it has not struck our political system with a blow we cannot sustain. We are still standing.

What’s more, the notion of an election under siege, a ballot conducted under the gaze of armed men, also gives these pathetic young men – men so frightened of life that they make a target of little girls – far too much respect. It grants them too much power.

So let’s hope that the soldiers’ work is done by 8 June, and that they can be gone. We need our election to go ahead undisturbed, lest we give these murderers even the scent of victory.