In this globalised world, if we launch weapons of great destructive power into communities abroad, incinerating and shredding women and children, we cannot avoid the fact that those who identify with those communities – ethnically, culturally and religiously – will take revenge on people here. If we are lucky it will be revenge on combatants. If we are unlucky it will be on our innocents. But either way, the truth is this. We caused it.

We caused it by our invasions, occupations and bombings of Afghanistan, Iraq, Libya and Syria, none of which had ever attacked the UK. We caused it by all the dead women and children that British bombs, missiles or bullets killed accidentally. We caused it by the terrible deaths of the people we killed deliberately, who were only defending their country from foreign invaders, just as most of us would do. We caused it by the detainees killed or tortured. As a country, the United Kingdom caused it.

This is not the 19th century. Imperialist aggression now brings a danger of retaliation from empathetic communities embedded in western societies. This is so obvious as not to need stating. The danger of terrorism from Islamic sources would be much reduced if we just minded our own business on the international scene.

All that is very obvious. It does not, however, seem to have occurred to John Sawers, immediate past head of MI6, who has no sensible thoughts at all of the causes of terrorism. The right wing like to think that anyone opposed to the West is, by definition, spontaneously evil. If only they could look in the mirror sometimes and ask why people hate us, that would be a major psychological breakthrough. I have known John Sawers a great many years, and he is somebody who looks in the mirror very often. Sadly, not for that purpose.

At least he has the intellectual honesty to admit an open advocacy of the extreme big brother society. Abandoning the notion of smart intelligence, he has come out with a justification of the mass surveillance society which Snowden revealed. We cannot prevent terrorism without spying on innocent people, he declares.

In a sense, that is a truism. I have very often argued that it is impossible to prevent all evil and daft to try. You have a far, far higher chance of being murdered by a member of your own family than you have by a terrorist. Over the last 10 years terrorists have been responsible for almost exactly 1% of all murders in the UK. Let me type that again. In the last ten years terrorists have been responsible for almost exactly 1% of all murders in the UK. And about 0.007% of woundings. It remains true that the most likely person to kill you is in your own family. It is worth remembering that the number of people who died in the Charlie Hebdo atrocity was the same number murdered in France on average every week.

Now assuming the aim is to prevent murder rather than make propaganda, let us concentrate for a moment on – don’t worry, you will never in your life be asked to do this again, unless by me – let us concentrate on the 99% of murders which are not by terrorists. To take the John Sawers system, if we had permanent CCTV monitoring of every kitchen in the UK, we could probably prevent quite a few of those murders and a vast amount of non-fatal violence. It would take an enormous police and security service, of course, but we are getting there anyway. Sawers’ point is completely correct in logic – you cannot prevent all murders without massive surveillance of the innocent. It would have been even more correct if you just stopped the sentence at you cannot prevent all murders. Precisely the same is true of the tiny risk to individuals that is murder by terrorism.

The surest way to reduce the terrorist threat in the UK is to stop bombing or invading other countries. That simple fact needs to be screamed from the rooftops. The next thing you can do is solid old fashioned evidence-based police and intelligence work. The least effective thing you can do is simply trawl the email and online chat of millions of people. That clogs up the intelligence system with a vast mound of undigestable information, and results in the conviction of fantasists and boastful men who, while unpleasant, are guilty of nothing but thought crime. It is exactly the same result as if you tackled murder by arresting everyone who in an email or chat wished harm to their husband or wife. It is wrong to express that, but the percentage who would have really gone on to murder would be vanishingly small.

The great worry is the presumption which is sneaking in to the mainstream media narrative that it is the responsibility of the state to prevent all crime before it happens. It is not, and that is not an achievable goal. The restrictions on liberty it would entail would do more damage to society than crime itself, which mankind has managed to live with since civilisation began. The entire debate around terrorism needs to be recalibrated. The answer is not the ultimate Big Brother surveillance state. The answer is to stop our hideous violence towards communities abroad.