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Last week many Britons were amazed to read in the quality press that the UK's nuclear weapons are thought to have a "design fault" which could see a transport accident detonating multiple warheads in a devastating chain reaction apparently known as "popcorning".

"More than 1,700 warheads are affected by the problem which would cause them to explode one after another," trumpets the Daily Telegraph. Holy Crap.

The manual was "seen by New Scientist", as the Telegraph notes, lending the story a frisson of newsworthiness - no doubt Edwards was shown it by a worried whistleblower, or perhaps a mysterious Deep Throat-style insider source.

The document apparently says that the present impact-safety standard for warheads is "single-point". That is, the warheads cannot be made to go off or partially function by a violent blow, or a succession of blows, as they might sustain for instance in the case of falling off a crane.

However, the MoD nuke boffins say that a recommended "design objective" should be to produce warheads which can provably resist multiple simultaneous impacts from different directions. It isn't that the current ones are thought likely to go off in such a scenario; it's just that you can't prove they won't, as this wasn't part of the design spec.

Not really a design fault as such, then. Tomorrow's cars will be safer than today's - do today's therefore have design flaws?

As for popcorning, you can't say that would happen - or how much it would happen - if one warhead partially functioned close to others, but it's at least theoretically possible.

"For popcorning to happen, a significant number of specific and unlikely events would need to occur in sequence," the MoD said in a statement. "The likelihood of this sequence of events occurring is incredibly remote."

So it could happen; but realistically it would make more sense to worry about a rogue submarine crew firing the weapons on purpose than a popcorning accident. Indeed, it would surely make more sense to worry about a rogue prime minister, or a rogue head of a different nuclear-armed state with a grudge against the UK.

But "the effects of a popcorning accident would be dire," says Edwards. "In the worst-case scenario, people a kilometre away would receive a radiation dose of 100 sieverts - that's 16 times the lethal dose."

Dire indeed - though not in the same league as a warhead actually functioning as designed, and immensely less likely. Popcorning requires many implausible events to happen in sequence, then yet another multiple roll of double sixes has to occur for the effects to become serious. An undetectably insane or simply evil person or group of persons getting firing authority somewhere is likelier.

Still, secret MoD nuke documents are always interesting. Although these ones aren't actually secret; without giving details, Edwards admits that the manual he quotes was "declassified last month".

In fact, a redacted copy of Joint Service Publication (JSP) 538 Regulation of the Naval Nuclear Weapons Programme was placed in the House of Commons library last month in response to a Parliamentary question. You can't read it online, though; it's hard copy only.

Only someone with a very good reason would go and read an entire fist-chewingly dull MoD manual and then struggle so desperately to squeeze a scary headline out of it. Funnily enough, Edwards has just such a reason. He is a former leading light of the Scottish Campaign to Resist the Atomic Menace, a former CND campaigner, and the co-author of Britain's Nuclear Nightmare and Still Fighting for Gemma.

The latter work focuses on the harrowing death of a young girl from leukaemia, and lays the blame squarely on atomic power. It's a simple message: Nuclear technology equals little children dying in agony. Be afraid and horrified.

In more recent times, Edwards has tended every year to dredge up a dusty MoD publication and run a scare story during the summer news drought. Last year it was "UK nuclear accidents blamed on poor safety". In 2006 it was "Road Crash could set off Nuclear Blast".

So "popcorn warhead design fault will lead to innocent kids dying in agony" can probably be filed in the same place you'd file "terror threat means all civil liberties must be suspended", "reefer skunk death puff will make your kids go insane", "drinking booze is the most evil thing you can ever do". Etc, etc.

In fact, it might be best to just stop reading the news for the next couple of months always check the Reg for the unvarnished scoop. ®

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