The terrorist atrocities which France has suffered in recent days could well happen here: Andrew Parker, the head of MI5, warned, in the speech he delivered on Thursday, that “an attack on the UK is highly likely”. His calm analysis is worth reading. The tone is reassuringly sober, and so is the content. For he does not pretend that only by giving our security services more and more powers can we hope to sleep safely in our beds.

Parker does make the case for enabling his people to intercept the communications used by would-be terrorists to plan attacks. Our security services must be allowed to keep abreast, within a robust legal framework, of the technological changes which might enable our enemies to conceal their malignant schemes until it is too late. But he also says:

“even when violent intent is solely the work of one individual and they share their specific plans with no one else, it is almost always the case that someone, a member of the public or a friend, has had some prior insight into the dangerous direction they are moving in and the violent destination they are hoping to reach.  So, as we go forward into 2015, we will need more help from the public in these sorts of situations.”

If the horror of what has happened in France increases the flow of such intelligence, some good will have come of it. As in all terrorist campaigns, the battle is for hearts and minds. Parker observes that “terrorist-related arrests are up 35 per cent on four years ago”, and that since 2010, “more than 140 individuals have been convicted of terrorism related offences”. But he goes on to say:

“it’s an even greater success when individuals faced with ISIL’s propaganda turn away from its twisted message. We have seen the human misery that results from the opposite choice: bereaved and broken families, ruined lives, suffering and heartbreak.”

The battle for hearts and minds will take a long time to win, and there will be setbacks along the way, when abominable crimes are committed. But the enemy is plain in view. The contrast between civilisation and barbarism could scarcely have been made clearer. The need to defend our inheritance of freedom under the rule of law has seldom been more obvious. Our leaders have their task, which is to demonstrate, with patient resolution, that the law exists to protect everyone in this country, of whatever faith, against murderous terrorists who want to take the law into their own hands.