The attack at the Ariana Grande concert at Manchester Arena saw 22 killed and more than 800 injured. Suicide bomber, Salman Ramadan Abedi was killed instantly.
The explosion in Manchester yesterday could be confidently labelled terrorism before the cause was known or anybody had "claimed responsibility".
What a wretchedly inappropriate phrase that is.
Whatever would cause anybody to detonate a bomb in the foyer of the largest indoor arena in Europe, just as a young audience was likely to be coming out of a concert by a touring pop star, has no shred of responsibility. As for "claiming" it as though it were credit, only a sick or criminal mind would do so.
Terrorism of this kind has become so frequent in Europe over the past few years that the culprits hardly bother to post a public admission.
The carnage is immediately and universally attributed to the likes of Isis, which is never likely to deny it. The only question that matters (a little) is whether the perpetrator(s) were from an organised cell of jihadists or a lone local malcontent immitating them.
If Isis was behind the blast in Manchester, it may be a reflection of the fact that it is near defeat in what remains of its Islamic State in Iraq and Syria.
The "caliphate" it declared four years ago has lost almost all its territory but will no doubt fight on as a stateless underground network like al Qaeda.
Western cities may suffer more rather than fewer attacks when Isis has nothing left to defend and plenty of frustrated fighters turned loose.
The timing of the latest bombing raises the possibility that it is a response to Donald Trump's visit to Saudi Arabia.
The trip has moderated the rhetoric of Trump's election campaign on the subject of Muslims and the threat they pose to the United States. The amiable tone of the visit will not be to the liking of those whose cause and recruitment depends on a climate of mutual antagonism, suspicion and distrust. Every terrorist incident makes it harder to argue for tolerance and diversity in Western democracies.
Image 1 of 14: Armed police work at Manchester Arena after reports of an explosion at the venue during an Ariana Grande gig in Manchester. Photo / AP
But if the Manchester atrocity follows the pattern of attacks in Berlin, Brussels and Paris in recent times, the terrorism was probably home-grown, a result of festering resentment within second generation migrant communities.
The perpetrators may be Islamic by heritage rather than active religious belief. They are probably using Islam as a badge of defiance of the values and authority of the dominant culture rather than living by its dictates and disciplines.
In every city and country there is no shortage of lonely and bitter individuals with a grudge against the world.
When the internet offers them the chance to make common cause with a frightening foreign idea, they are liable to adopt it. There would be many more explosions like that at Manchester if police and intelligence agencies were not keeping a close eye on these sorts of individuals and their associates.
Every terrorist incident is a surveillance failure of some sort and an inquiry must look for improvements.
But that should not blind us to the fact that in populations the size of Britain and the United States, we could expect many more deadly attacks than there have been. Each one is a reminder that vigilance cannot be relaxed.
