Truth about terror: The hysteria over Mohammed Emwazi disguises a crucial fact – that some terrorists will always get through

Could the British security services have done more to prevent Mohammed Emwazi embarking upon his murderous career?

He was, as the phrase goes, “on their radar”. He had even been approached to work with them while he was in Tanzania, and he had been under surveillance.

It is possible that Emwazi might have been placed under some control order, and confined to the UK. That, though, would still have meant he was broadly at liberty in this country, and it might not have been difficult for him to commit acts of terror here. As we saw in the murder of Lee Rigby, all that might be needed is a car and some knives. In that case, too, it is worth pointing out, the perpetrators were also known to the authorities. Much the same goes for the Charlie Hebdo attacks in Paris, and similar atrocities around the world. The beheadings that took place in Syria/Iraq would still have happened, with someone else murdering innocent people.

There is always more that can be done, and there is every point in the Commons Intelligence and Security Committee investigating this case, as it did with the Lee Rigby killers. However, in that case, the MPs concluded that there was nothing that could realistically have been done to prevent the murder.

The only sure way for the British security services to guarantee that a suspect will not commit an act of terror is to place them permanently in custody, without proof of a crime. Even with the draconian legislation we now have in place, that is not always possible. We would have to institute a limited form of police state, inevitably focused on one section of society, the vast majority of whom are law-abiding people who wish for nothing more than to make a decent life for themselves and their families. It would require vast manpower.

That degree of attention from the security services – spying, to use the old-fashioned term for it – would not be something that fostered community cohesion; it would almost certainly prove ineffective. After all, Osama bin Laden evaded the entire security apparatus of the West for a decade partly because he simply disconnected himself from all forms of modern communication. That is why it is wrong to blame the mobile phone companies and social media firms such as Facebook and Twitter for these crimes; it is impossible for them to police all the traffic that takes place on their networks, and terrorists can always evade detection.

There is a wider point here too, which is the understandably mesmerising effect of someone from a British background becoming the most prominent terrorist in the world. He is not, though, alone, and this is not a purely British phenomenon, even allowing for his family connections to Kuwait. He has many accomplices locally and globally, from many different kinds of societies, including, as it happens, autocratic regimes where suspected terrorists are routinely tortured and detained indefinitely without trial. Isis fighters are recruited everywhere from Sweden to Uzbekistan. It is a global phenomenon.

Of course, we should continually revise our terror laws and the resources we give MI5 and MI6. And yet, without being defeatist, it is true that some terrorists will always get through even when liberties are suspended. Did Guantanamo make much difference to the growth of Isis? Did internment without trial in Northern Ireland ever actually stop the IRA?

Isis is a tough enemy, and we need to understand much more about why some are attracted to this death cult. But locking up every young man or woman who seems remotely at risk of extremism is not going to work.