A golden rule of reporting crimes is to try to balance instant news and analysis against legal obligations and wider responsibilites – such as not prejudicing a trial and ensuring that coverage is proportionate.

And an established fact in relation to terror attacks in the west is that Islamist extremists are planning and executing them, and that one’s first instinct in hearing news of such a incident is to assume that they may be responsible.

While sticking to the rule this morning, I will try to put that fact into context in writing briefly about yesterday’s incident in Russell Square, in which a woman was killed and five people injured in a knife attack.

Such an assault is undoubtedly terrifying – though not necessarily a terror attack in the sense that the phrase is usually used: namely, one planned and executed by a terrorist group.

It may indeed turn out that there is a link between the 19 year-old man who has been arrested consequently, and Islamist extremism – even perhaps an Islamist terror organisation.

At this stage, the police cannot exclude that possibility.  They must duly say so.  And the media must draw on their view in its reporting.

But it is worth bearing in mind three other factors related to some recent terror attacks.  The first is mental health.  For example, the perpetrator of the Orlando massacre and of Jo Cox’s murder evidently had or have mental health issues.

It is therefore worth noting that the police statement about yesterday’s crime says that “early indications suggest that mental health is a significant factor in this case”.

The second is drugs.  Past or present use appears to have been a factor in lives of those who carried out the recent Munich and Nice murders, for example.

The third is a dysfunctional family background, and perhaps a criminal record.  Consider the case of the el-Bakraoui brothers, who carried out the assaults earlier this year in Belgium, for example.

In short, Bernard Hogan-Howe is right to warn in relation to another terror attack in Britain that it’s a case of “when, not if”, and it is doubtless necessary for the police to step up their presence.

But it is important to bear in mind that not every assault claimed in the name of Islam was planned by a terror group in Raqqa or elsewhere.

And it is worth remembering that the combination of mental illness, drugs and family breakdown can itself drive crime, and that Islamist ideology is not necessarily a fourth factor.

There’s an Islamist theat, to be sure.  But caution is one thing; panic would be quite another.  The personal risk to most Britons of being caught up in a terror attack is low, at least at present.

Terror is terrifying.  That’s its point – why terrorists carry out terror.  But there’s no need to make it more terrifying than it already is, and every need to keep calm and carry on.