The first is that, clearly, any threat from Islamic militants to Europe may rise and fall, but does not disappear when a single figure is arrested, however much he was sought. The “major blow” struck on Friday, as senior policymakers called it, now looks less major.

The second is that both terrorists and those trying to stop them seek to keep the initiative. This has a practical and a psychological aspect. For counter-terrorist agencies, the aim is to get information fast enough to mount raids and sweep up suspects before they even have time to work out who among them has been picked up and who might have talked, let alone plan a new strike. Networks quickly fall apart under such relentless pressure, as was shown in Iraq in the middle of the last decade.

For the terrorists, the aim is to show they can still terrorise, mobilise and polarise with violence. This is not so much about revenge, but simply demonstrating a continued capability. They may be down but, they are saying, they are not out.

It is also very possible that the extremist network wanted to act before security agencies acted on any information divulged by Abdelslam, who is known to have backed out of a suicide attack and may have been considered by his erstwhile co-conspirators as likely to cooperate with authorities.