The gravitational pull that Westminster has on London mirrors that which the capital itself has on the rest of the country.  Britain’s political and media elites are concentrated there.  So if a man runs amok with a car and a knife, some of them will see it happen and, security at Parliament being as it must be, many of them will be affected.  This site’s own Andrew Gimson was one witness, preparing a report for this site from Prime Minister’s Questions as the incident happened.  It will be reported as an assault on the heart of our liberal democracy.

So it undoubtedly was, and it is right to mourn the loss of Constable Keith Palmer, praise the courage of Tobias Ellwood and honour those killed yesterday on Westminster Bridge.  But it is necessary to add that the incident will win more coverage and commentary than it would have done had the same number of people been killed and injured in a similar attack in another city or in provincial Britain.

The main reason for this is not metropolitan bias – mostly, anyway.  It is that the cameras and tweeters would not have been present in such numbers elsewhere.  It would almost certainly have taken the police longer to get to the scene: yesterday, they were not only on the scene but, in a sense, were the scene – apparently, a special target for murder.  The impact of the incident will therefore be less in much of the rest of the country than it will be in the capital.  Most people will be horrified by what happened, grasp the killer’s intention, and stand in solidarity with the parliamentary government that he presumably hated.  But to love our symbols is not necessarily the same thing as to love our system, and it is necessary to add that a minority will be indifferent to yesterday’s horror, and that a smaller one still will mutter, Ellwood’s heroics notwithstanding, that our politicians had it coming to them.

And just as it is easy to project the natural agitation of MPs, Parliamentary staff and lobby journalists yesterday, or the twitchiness of some London commuters this morning, onto people in other cities or places who are unlikely to feel it, so it is possible to be panicked into thinking that everyone, everywhere is at risk.  This simply isn’t true.  The identity and motivation of the murderer have yet to be confirmed, but the way in which he acted, using first a car and a knife as a weapon, bear all the hallmarks of Islamist terror.  There are echoes of last December’s lorry-driven assault on a Berlin Christmas market.  The security services and others vigorously debate whether such attacks are more likely to come from “lone wolves”, urged to strike by groups such as ISIS, or whether the animals in question will be part of a wider pack.  It looks as though it will not take long to find out in this case.

Certainly, there is a real risk of a mass attack, especially in London, by terrorists with bombs and guns.  One could happen while this article is being written – or at any time.  Our intelligence agencies and the police have done brilliantly over the past ten years or so, succeeding in preventing a big-scale incident where others abroad have failed.  Sooner or later, other terrorists are likely to get through.  But it is worth remembering that yesterday’s incident was the first successful one on a public target in Britain since the Glasgow Airport assault ten years ago, and the first to take civilian lives since 7/7 in 2005.  And, mercifully, the killer does not seem to have had a gun with him, or to have been primed with a device.  Paris and Brussels have seen co-ordinated attacks by gangs of gun and bomb-wielding terrorists.  To date, London and the rest of Britain have been spared that.

On occasions like yesterday’s, it is in the nature of TV, with its live pictures and shaken bystanders, to project a sense of panic.  Twitter may instead be largely made of words, but has the same smack about it.  Today’s newspaper front pages, by contrast, are rather more sober.  They clear space for accounts of what happened, as indeed they should, but that, in these circumstances, is precisely the point: they stick, by and large, to reporting the news, rather than demanding new security measures or emergency legislation.  This is evidence that we have learned a lot since 7/7 about Islamist extremism – including the indispensable lesson that it is driven not by whatever foreign policy we may have at the time, but because its proponents hate our way of life, Muslims who disagree with them, and indeed everything outside their fanatical zealotry.

In the wake of yesterday’s killing, Ministers must take another good long hard look at our anti-terror laws and practices.  But they should do so regularly in any event as a matter of course – continuing to reject, as they sensibly do, Blair-era type attempts to catch headlines and propose policies with which they can be, as he once put it, “personally associated”, such as locking suspects up for 90 days without charge.  And MPs should not and cannot be hidden away from the people they represent.  They stand for election knowing the risks to them and their families, or should do.  Some are attacked and survive, like Stephen Timms.  One has been assaulted and murdered – Jo Cox.  It is tough on their parliamentary staff and others who work on the Westminster estate or elsewhere, but that’s in the nature of public service.  Big Ben cannot be cocooned behind barbed wire.

There was comfort as well as horror present yesterday: the schoolchildren from Somerset who sang songs to lift spirits, David Lidington’s dignified statement, the staff who carried on quietly working away and, above all, Ellwood’s attempt to save the dying Palmer’s life. Is it out of place to note that the Foreign Office Minister is now unsackable, or to suggest a promotion when the next reshuffle comes? Perhaps. But we do so none the less.

It would be cheering were the death of Palmer, and the other policemen who died yesterday, plus the heroics of Ellwood, to spark a public reappraisal of our politicians and police.  However, it won’t happen – for good reasons and bad.  Most people will not be swayed from their usual course.  Come to think of it, maybe that’s for the best.  Yes, we should mourn and learn.  But we must also keep calm, carry on – and not lose our sense of proportion.