HAD THE FIRST of what could have been a “wave” of attacks on long-haul flights from this country not been averted, it would have been a hideous tragedy for thousands of victims and their family members. It would have sent a shiver through millions more and caused costly but probably short-lived economic disruption.

A second or third set of assaults would have been far more serious. Had the suicide-murderers pulled off the same deadly trick a few days or weeks later, when security services were still at maximum alert, the psychological impact would have been many times greater than the physical and economic damage inflicted. As has been seen in Baghdad, successive atrocities are inherently more terrifying than one-off events because they instil a sense of despair.

The propagandists and instigators of Islamist terror would have trumpeted these multiple mass murders as a great victory — and millions of horrified people would have agreed. But in this deadly confrontation, what has to be remembered is that the terrorists can never win. Their apocalyptic vision of a world violently subjugated to their benighted interpretation of the will of Allah is unattainable.

The goal of this singularly nihilistic terrorist movement is not to keep airline passengers from carrying their spectacles in cases and make them do without laptops and even, somewhat absurdly, books. It is to convince the societies that Islamist extremists seek to destroy that nothing — neither individual and collective vigilance nor the sophisticated resources of the modern state buttressed — can protect them and their way of life from fanatics who hold mercy in contempt and exult in killing themselves as they kill. That the only certainties are that whatever defences we mount, the terrorists will adjust their targets and their tactics to circumvent them, and that the more resilient we prove, the greater will be our danger because they will eventually master still deadlier methods of destruction.

Terrorism is the Islamist movement’s greatest strength, because small cells of thoroughly indoctrinated terrorists are, in this game, effective force-multipliers. In the countries targeted by al-Qaeda and its offshoots and imitators, they need only to recruit a minute proportion of disaffected Muslim youths to have an impact way out of proportion to the loyalty, within that country’s community, that the extremists in fact inspire. In Britain, even if 99 per cent of the Muslim community were resolutely set against Islamist terrorism — a higher proportion than polls show to be the case — that would still leave a potential base of 15,000 in a population with a higher than average number in the 16-25 age bracket.

The bloody infantry of terror is not necessarily poor; not only in the West, but also in the Arab and Asian worlds, the terrorists’ “star” recruits tend rather to be relatively well educated, resentful young men who see Muslims as the modern world’s losers and are seduced by the idea of “holy revenge” against the forces that, they have been persuaded, have defiled the purity of the “City of God” through the spread of man-made law and secular authority, and thus denied Islam the supremacy anciently willed for it by Allah.

But reliance on terrorism is also the great weakness of Islamist extremism. To remain undetected, these cells must be self-enclosed and obsessively secretive. Successful guerrilla movements “swim in the sea of the people”, as Mao Zedong famously put it. Even where terrorists attract admiration, they end up by wrecking the home base. The more attacks they launch, the greater the harm to other Muslims, either because terrorist attacks are deliberately indiscriminate; or because, as in Luxor, Marrakesh and Indonesia, their targets are not only tourist infidels but the “corrupting” tourism industry upon which millions of livelihoods depend. There is no modus vivendi with groups that define all those who question their obscurantist distortions of Islam as “enemies of the Faith” and consider compromise a mortal sin, so societies have to choose. Once these cancer cells have become established, it may take long and terrible civil wars, as it did in Algeria and may in Palestine and, yet again, in Afghanistan, to wither them. But Islamist terrorists cannot ultimately rely on acquiring critical mass, the secret of all successful revolutions.

In its confrontation with the West, Islamist terrorism suffers from another weakness, one that its adherents do not recognise, and that anxious Western publics may also not see. It does not understand its enemy.

It may not look like that this week. Is not the boot on the other foot? Do not open and free-moving societies present wide-open targets to ruthless agents whose mindset is too alien for us to penetrate? This week’s impressive intelligence and police operation must strike many people as a success that only brings to mind the proverbial needle in the haystack.

Yet we know in broad terms what we mean when we talk about defending ourselves. They do not know what it would take to subdue us — if, even, they know what that means beyond depriving moderate Islam of friends or protection — because they do not want to know who we are. They are blinded by the virulence of their hate.

We have observed with alarm how Islamist extremists have warped the minds of young people who have grown up apparently well adjusted to British life. In the course of their indoctrination, there comes a point when their previous loyalties and affections are blanked out, rejected as the detritus of the time wasted before they became mustanbat, armed warriors of Allah. Recruits to Islamist terror are drilled in contempt as well as loathing for the cowardice, decadence and moral corruption of Western societies. But the cities of the damned are not as devoid of backbone as they are taught to believe. The “weeds in the Garden of Allah” have tough roots.

Extremism contains within itself the forces of its own destruction. Islamist terrorism has funds and adherents in plenty. To say that Islamist terrorists cannot win is not to underestimate the dangers they pose or the difficulty of keeping the threat within manageable proportions. Its agents will strike again, and they may land more than one hammer blow. But it cannot overwhelm the West; and it has nothing to offer Muslims but violence and delusion. The doctrine is bankrupt. This is a movement at war with the human instinct for survival, an instinct that has never failed eventually to prevail.

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