Europe has endured seven acts of vehicle terrorism in the past year, and the Barcelona killer was apparently able just to walk away. What on earth can be done?

Events yesterday in Calatonia suggest that, as with the London Bridge attacks of last spring, police are getting better at responding to these acts of carnage. The swift erection of barriers and the summary shooting of the Cambrils suspects will revive calls for more road blocks and more armed police. In the short term this will be hard to resist, as are calls for ever deeper intrusion into electronic communication.

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Yet the balance must be maintained, between personal liberty and what is, in reality, a highly uncommon threat. That its perpetrators are by definition immune to deterrence makes the menace more horrific, but also near impossible to reduce. We should perhaps remember that acts of “shock and awe” have also been employed as weapons by western governments, from the second world war to Iraq. There is a sense in which the white van is the poor man’s guided missile.

There will be much debate on how far we want to go in guarding the public realm without “terrorising” it. Parts of central London already look cowed and afraid, as ugly barriers go up around tourist sites. For decades we have not separated pedestrians from speeding and drunken motorists, despite the resulting death toll. We should not vandalise streets and deface cities to avert the tiny risk of deliberate rather than accidental death.

The obvious response is to repeat that an evil act whose execution cannot be prevented had better be regarded as unavoidable. London in the 1970s and 1980s came to accept IRA bombs as almost part of living in the capital. It would help if grotesque publicity were not given to these acts of terror. It distorts risk, encourages imitation and undermines freedom from fear. How to report yet not “promote”, how to convey sympathy without propagating fear, is a skill at which the media is all at sea.

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On a different plane, these acts should remind us of the fragile compact on which a peaceful society is based. As we have seen this week in Charlottesville, violence is never far below the surface of group hatred and fear, the ugly face of “identity politics”. It is a platitude that communities must be more vigilant, must report oddballs, must be on guard. The only real crime prevention is at source, which is why the government’s much ridiculed Prevent strategy has to be right in principle.

The uncomfortable fact is that almost every act of terror has a political component. The politics of conflict cannot be entirely swept under the carpet of crime. We are still militarily engaged in Muslim states – which many are bound to see as a war on Islam – and seem unable to stop ourselves. Tragically, all wars have casualties.

• Simon Jenkins is a Guardian columnist