Deep in his heart, every Englishman suspects that someone is trying to poison him. He is not absolutely sure who, how, or indeed whether — perhaps he is imagining it; but then again ...

Poisoning people is one of the oldest means of attack known to man but it has been decisive in no war in history. What power it has stems from a capacity to frighten and demoralise. Nothing suits a subversive cause better than rumour, assisted from time to time by a small item of hard news, that a conspiracy to poison us is afoot. The news this week from Wood Green has been, for terrorism, a public relations coup. The operation has cost little. The guilty, if they are identified, will turn out to be small fish: dispensable to their masters, if they have masters. How weird that our media should have joined them in converting this pathetic squeak into the roar of front-page headlines. It confirms my belief that the Anglo-American alliance and al-Qaeda now need each other badly.

Both know the hold which that word “poison” has on the English-speaking imagination.

We are at once horrified and fascinated by the idea. It could be a close friend, a malevolent neighbour, a jealous lover, an irresponsible food corporation, a foreign government or a shadowy terrorist network. It could be something in the water or the very air we breathe; it could lurk in a baked potato or be slipped into a drink ... among the many means of attack available to those who wish us ill, be in no doubt that in the English imagination poisoning is the option which really chills the blood. Any columnist knows the disturbing number of his readers who think that death-rays are being emitted by their television sets.

I use the term “poisoning” in a wide sense: the invasion of our bodies by something invisible or slight, which will then attack us from within. Unlike an obvious assault from without — by fist, knife, explosion or bullet — there is horrid secrecy about poisoning: the means of our own destruction, insinuated into us.

Freud would have an explanation for the grip which poisoning has upon the human imagination. Our fixation with laxatives and purgatives — our morbid interest in bulimia and colonic irrigation — is bound up, I believe, with the same cluster of instinctual horrors: we stand aghast at an enemy implanted within. Fear of CJD is in the cluster too. So was the national panic about the MMR vaccine, and our worry when the Prime Minister would not say whether his own son had been vaccinated.

It would be a rash columnist who dismissed as mere scares every worry about GM foods, carbon dioxide levels or lead poisoning in car exhausts. We may be sensible to fret about fast-food adulterated by big corporations and a limitless range of things which may give you cancer, but what tabloid editor could deny the unreasoned appeal of a poisoning story, regardless of its evidential base? Leakage from atomic reactors (or microwave ovens), irradiated food, biological washing powder, nuclear waste, brain tumours from mobile phones, leukaemia from overhead power lines, all these write their own headlines. One of my grandmothers even thought the night air might be poisonous.

Radon gas from the rocks beneath us, skin-cancer-inducing UV rays from the ozone-depleted atmosphere above, and the possible side-effects of every kind of drug, scare us so easily. Reasonable or otherwise, alarm wells up before reason has been consulted. Burgeoning concern about adulteration by food preservatives, and about allergies of every kind, are part of the same primitive fear we have of ingesting, absorbing, breathing, being bitten by or being injected with something toxic. Lucrezia Borgia could never have achieved her infamy with a sword. Though the scorpion’s sting rarely kills and the snake is a timid creature, animals which make a beeline for our blood- stream cause a special shudder.

Parasites, intestinal worms, jigger-flies, spiders which lay eggs under our skin ... aargh! Viewed as a communications tool, therefore, the word “poison” is fabulously potent. Just try rolling around your tongue words like “toxic”, “arsenic”, “cyanide”, “acid”, “hemlock”, “anthrax” ...

Or, since Wednesday, “ricin”. That mysterious entity, “the al-Qaeda high command”, must (if it exists) be jubilant. A makeshift kitchen operation above a shop in North London, using beans from the common castor-oil plant to make a concentrated poison (something any half-wit with a handful of beans and a biochemistry textbook can do) has been rocket-launched into a major scare and chilling testimony to the potency of al-Qaeda. So now we know. Osama plans to poison us, one by one or all at once.

Let us pass over the fact that the “links” with al-Qaeda (someone is “linked to” anything commentators say he may be linked to — by them) are speculative. Pass over the fact that anyone ever offered advice by someone claiming membership of al-Qaeda is now said to be “al-Qaeda-trained”. Pass over the fact that the Wood Green suspects appear to have no connection with Iraq. Pass over what we know about a whole range of Algerian sects whose goals are domestic.

Pass over the fact that the more Tony Blair and President Bush puff al-Qaeda the greater will be the temptation for any crackpot terrorist cause to link its aims with a big and famously terrible organisation.

Pass over the fact that ricin is the very opposite of a “weapon of mass destruction”. It is a weapon of individual assassination. A man with a machinegun in a crowded theatre is closer to a WMD (whatever that moronic acronym now chanted like some kind of Shinto mantra may mean) than a teenager with a phial of bean pulp in a North London kitchen. Pass over the fact that ricin is anything but a new discovery, has been studied as a potential weapon for decades, and never yet thought to merit a major place in anyone’s arsenal. Pass over the fact that you can buy guns easily here or hire a hitman for about £5,000.

Times Recommends

• The ghost of Robin Cook haunts Chilcot’s feast
• The truth shouldn’t need oaths
• Violence: let’s separate the men from the boys