The habit is more disliked by listeners and readers than I think editors appreciate. Perhaps the first item on each day’s news agenda should be “matters arising from yesterday’s news”. News editors would then do us the courtesy of explaining where some of those stories went.

Immediately after July 7 it was prominently reported that the explosions “bore all the hallmarks” of the use of a type of high-grade military explosive whose presence would indicate a sophisticated international dimension to the bombings. We were alerted to a likely al-Qaeda link.

Then the news went silent. Then it was announced that tests showed the explosive to be of a home-made (or home-makeable) kind that al-Qaeda were known to know about from the internet. Then that story, too, seemed to fizzle out.

I have seen no explanation of how the initial assessment of the type of explosive could have been the reverse of the truth, and no acknowledgement of error from those who made it. Nor has the al-Qaeda/internet angle been followed up. The most recent assessments (Kevin Toolis in The Times yesterday) have suggested that there was nothing special or “hallmarked” about the explosive at all.

Immediately after the first bombing, a report was splashed that two people had been arrested trying to leave Heathrow. The later report that they had been released without charge appeared as little more than a footnote.

A few days after that, much was made of the arrest in Egypt of a British Muslim whom the less-scrupulous news reports called a “chemist” (he is a biochemist). There was talk of British agents attending (or joining) his interrogation in Cairo. A statement from the Egyptian authorities denying that they had linked him to the bombing or that he was on their list of al-Qaeda suspects, did receive momentary attention — and then the story seemed to die. I do not know what has happened to it, or him.

Then there were some big headlines about an alleged “al-Qaeda operative” who had “slipped” into Britain, and slipped out — just before the bombings. But it transpired that he was low on our counter-terrorist services’ lists of security threats — and that story, too, has disappeared.

Then there was an arrest in Pakistan of an alleged “al-Qaeda mastermind”, about which reports have become increasingly confused, dropping from their early position as leading news items. I do not know where we are now on these reports. If I understood them correctly, what helped to trace this mastermind were records of calls made to him by all, or some, of the four July 7 bombers from their mobile phones.

If anyone has asked (or answered) a question that surely occurred to millions of us, then I have yet to hear of it: why did the bombers not take the elementary precaution of phoning the mastermind from a telephone box? Just how master was this mind? Is it not a curious way of operating a terrorist network, if the terrorists are to call their mastermind on their mobile phones, then take the phones with them on their bombing spree?

This is only a small sample of the deadends (or possible deadends) in the July 7 and July 21 stories. You will have noticed many others. You will notice, too, that every one tends in the same direction. Each report, when first we read it, accentuated the impression that we face a formidable, capable, extensive and well-organised terrorist movement, with important links abroad, and that is almost certainly being masterminded from abroad.

And indeed we may. Nothing — I repeat, nothing — I write here is meant to exclude that possibility. Some of the scares that grip our headlines and imaginations do later turn out to have been every bit the threat we thought they were. I have not the least idea what may be the size, shape and competence of al-Qaeda and would not dream of suggesting (and do not believe) that they are uninvolved.

Nor do I mean to downplay the horrors that have hit London: death and destruction are death and destruction, whoever causes them.

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