The threat of young Isis converts may be impossible for intelligence services to stamp out

It is naïve to imagine that determined Britons can easily be prevented from joining the battle in Syria and Iraq

The security services insist that the tracking of British jihadists returning from Syria and Iraq is now their top priority. Given that young men from the UK have been fighting in the Syrian conflict for months, this news raises the question: what was their top priority before?

The emergence of Isis may have changed the game for Britain’s security chiefs, but a sceptic might wonder whether the apparent recalibration has as much to do with the fact that a Western-backed government in Iraq – rather than a Russian-leaning regime in Syria – is now the subject of attacks.

Putting to one side the motivation for this apparent shift in focus, it also has to be asked whether the “tracking” efforts of the security agencies will have real impact. It seems implausible that MI5 can keep tabs on every person who returns to the UK after fighting in the Middle East – and was declared as such by a former director of global counter-terrorism at MI6. That is not to say the task should not be attempted. Yet it feels like an old-fashioned response to a threat that has an increasingly contemporary character.

Likewise, it is all very well for the Home Office to promise that the existence of terrorist and extremist propaganda online will not be “tolerated” but what does this mean in practice? Once again, it sounds like institutional recourse to platitudes of the distant past.

Isis, conversely, has promoted its agenda precisely by presenting itself as ultra-modern. Its foot-soldiers do not march through the desert; they drive in sleek 4x4s. Recruits are not seen in grainy video footage reading from scripts; they are shown in sleek, high-definition clips. Social media and the World Cup are not ignored as Western fallacies; they are harnessed to the propaganda cause. Isis and their ilk may be opposed to modern liberal values, but they are not the enemies of modernity per se. To some young, bored Muslims in Cardiff and elsewhere, Isis must seem a lot more 21st century than anything British public life has to offer.

The UK’s security services do a hard – sometimes impossible – job and they deserve enormous credit for the fact that terror attacks on British streets have been relatively rare since the London bombings of 2005. Nevertheless, there has to be a sense of reality about the threats posed by Isis and its British followers.

It is naïve to imagine that determined Britons can easily be prevented from joining the battle in Syria and Iraq. It is other-worldly to believe that the slickly produced, cleverly packaged Isis propaganda videos can be wiped from the internet. And while tracking jihadists on their return is all very well, if the threat they pose to British security is as significant – and if they number as many – as we are warned, then it may prove as difficult a task as chasing shadows.

Isis carries a strong appeal to a tiny proportion of British Muslims. To talk of a battle for hearts and minds creates an uneasy echo of the maxim of UK armed forces in Iraq and Afghanistan. But it sums up the key imperative in all this: Isis wants to induce young Western Muslims to take up the cause of jihad; British authorities – and society more generally – must do all they can to persuade them of the moral case for not doing so. To begin with, we must change the narrative in which the individuals involved are described as “vulnerable”. They may or may not be. But the last thing they want is to be patronised.