These politicians seem to have decided that the problem of how to stop terrorism is best approached through the prism of common delinquency - like, say, crime on the Paris Metro.

That approach is certainly easier than putting more effort into grass-roots policing, fixing overcrowded "jihadist school" prisons or trying to turn around the French suburbs, where poverty both material and spiritual underpins social exclusion, chronic failure at school and high unemployment across three generations of post-colonial immigration from North Africa. But those are the real challenges.

A good example of the limits of the "delinquency" approach is the southern French city of Nice, where on July 14 an Islamic State-inspired lunatic ploughed his truck into Bastille Day crowds, killing 86 people. Nice, troubled by what the French call "inter-community tensions", reportedly has more security cameras and municipal police per head of population than any other French city. But that did not stop the attack.

Last week, despite the state of emergency in Paris, a member of the public telephoned police three times about an unregistered car full of gas cylinders, parked with its lights flashing for several hours about 100 metres from Notre Dame. French authorities later confirmed the abandoned vehicle was part of a failed terrorist attack in the much-visited, supposedly highly securitised precinct of central Paris that is also home to city police headquarters, at 36 Quai des Orfevres, just a few streets away from the famous cathedral.

But the ultimate paroxysm of summer myopia came with heated discussion of the burkini, the bathing suit designed in Australia which some 30 French towns and municipalities have banned.

It is not known how many French women wear it, but the polemics over it have lifted sales, according to a French Channel 5 television program, by an extraordinary 200 per cent.

Some 1500 to 2000 women are estimated to wear the burqa or niqab, French experts say: one-third of them due to modesty; another third for reasons of identity ("I want to show I'm Muslim") and the remainder because Islam says they should. None of them have been linked to terrorism.

Nobody really believes a burkini ban is an efficient means of dealing with terrorism, of course, but there are polling points for politicians who back the ban, even if it puts police under pressure, raises inter-confessional anxiety and places France on the same side of the argument as Muslim countries from moderate Morocco to hard-line Saudi Arabia, where women who wear the burkini risk stoning.

The spectacle of the French political reaction to bathing suits plays straight into the hands of the demagogues who believe the West is anti-Muslim and that exploiting the notion of Muslims as victims is an effective method of building a transnational political movement.

Other terrorist acts in the European summer deeply traumatised communities in France and Germany: in Bavaria, a man knifed an Asian family on a train and another man detonated his backpack of explosives outside a music festival.

In France, after the maniac in the truck, two terrorists murdered an elderly priest in a Normandy church after taking worshippers hostage during Mass.

French President Francois Hollande reiterated his recent bellicose rhetoric after the Normandy atrocity ("We will win this war"), though there were no fighter planes or ships involved; rather, French men slitting the throat of another French man in a church in the village they shared. The echoes in fact are of Europe's Wars of Religion or a civil war, given that both attackers and victims were homegrown.

Still the evocation of war in any form is probably not the best way of getting an intelligent fix on what to do about the terrorism threat.

As sociologist Laurent Mucchielli has pointed out, when the danger of an attack is present it may already be too late, because these people (unlike delinquents in the Metro) want to die. Investigations into the attacks in France since Mohamed Merah murdered seven people, including three Jewish children and a rabbi, in 2012 - the first jihadist killings on French soil in 16 years - show that the perpetrators were planning their actions months in advance, which gives the lie to theorising about marginalised "lone wolves", sitting at home in front of screens without networks.

Each time there were signs an attack was in the offing, seen by the likes of neighbours, apartment block managers and shopowners. Catastrophically, the last to be informed were often the local police.

Former French president Nicolas Sarkozy, perhaps France's most shamelessly opportunistic politician, has led French calls for a nation-wide burkini ban and pledged to introduce one if he is returned to the presidency in elections next year.

He is also the politician who, in the Elysee Palace for five years until 2012, dismantled and disorganised the kind of grinding, proximity policing best suited to detecting dangers early in the piece.

It seems the current French government has failed to take the measure of those decisions, which now look to have been a major mistake.

Richard Ogier is an Australian journalist and former Australian embassy press attache in Paris.