These killers cannot be eradicated. Though they pose a threat to human lives they do not threaten Western values. They may stir dictatorial tendencies in paranoid politicians. But to imply that such incidents undermine freedom is to lose all faith in democracy. Whatever the motives, these are criminal acts. They should be met by the art of intelligence and the science of security, not by the crass hand of “regime change”.

I must have read a million words over the past year about the threat of weapons of mass destruction. Tony Blair believed this threat so awesome and so urgent that last month he sent the British Army to war. The casus belli was bogus and was all but abandoned within days of the “war” ending. Two of Mr Blair’s once trusted colleagues, Robin Cook and Clare Short, have resigned from his Cabinet in protest, accusing him of lying to appease Washington and to secure “his place in history”.

The 29 or more deaths and 200 or so injured in Riyadh are a reminder that the present danger comes not from the fantasies of right-wing presidents and prime ministers. It is not from an “axis of evil” or some Doctor No plotting global holocaust in a secret desert laboratory. Nor should we honour these killers with such exaggerated status. There is no evidence that they are backed by a ruthless dictator, nor that toppling another hapless regime will do anything to stop them.

The Riyadh bombs, like last October’s Bali bombs, are technically no advance on the weapons used in the last rash of such attacks in the 1970s and 1980s. The terrorist’s purpose, we should remember, is not to kill as such but to create high-profile mayhem. For that purpose nothing beats high explosive. The bomb in a crowded space was the preferred weapon of the Zionist Stern gang, the IRA, Eta, the PLO, the Red Brigades and of separatists everywhere. A suicide bomb is near impossible to defend against. It needs only a stick of dynamite and the deranged anarchist of Joseph Conrad’s Secret Agent, moving “unsuspecting and deadly, like a pest in a street full of men”.

If no vigilance can guard against the bomb, vigilance is essential against the bomber. It is the deployment of human intelligence. A congressional inquiry is now under way into the failures that appear to have preceded September 11. This inquiry, conducted during an election run-up, is likely to be ruthless and bloody. Present British critics of America should note that such an inquiry is inconceivable in London. Ministers such as Jack Straw and Geoff Hoon would assert “reasons of state security” for silence and secrecy. The Franks Report into the original Falklands debacle was hopelessly nobbled. Yet only through public investigation of failure can future disaster be averted.

The Saudi bombs are being attributed to the al-Qaeda network of Osama bin Laden. If so, we might reasonably ask for an inquiry into why two colossally expensive and destructive wars were fought by the West yet left unscathed the architect of all this woe. Mr Blair explicitly declared that bin Laden’s capture was the purpose of the invasion of Afghanistan. He then alleged a “clear” link between Saddam Hussein and al-Qaeda as one of the pillars justifying the invasion of Iraq. I can see that the people of Afghanistan and Iraq may feel more free, for the moment, but that was not the point. The point is lying smothered in blood and rubble in Riyadh.

The British Government may argue lamely that more substantial weapons might have been unleashed had it not been for its bellicosity. According to this argument, presumably, the Riyadh bombs are the last gasp of a group running out of ammunition, money and state sponsors. I doubt it. The latest assessment of al-Qaeda by the International Institute of Strategic Studies is published today. It concludes that changes in the organisation since Afghanistan “could make it even more difficult to combat . . . more insidious and just as dangerous”. It’s now dispersed and thus more impregnable to infiltration.

A respectable school of analysts — not wimps, appeasers or “surrender monkeys” — thought the best way to spring bin Laden was not by bombing the hell out of Kabul but by bribery, corruption and possibly murder. Above all, it was important to keep him in the West’s sights. An equally respectable school, indeed most of the intelligence community, could find no link between Baghdad and international terrorism, however ghastly Saddam might have been to his own people. The fear was rather that unstable anarchy might follow invasion, a fear now close to being fulfilled.

As long as al-Qaeda is on the loose — with half the Islamic world regarding bin Laden as a liberation hero — the West is at risk of continued attack. All the bombs and missiles in the world have not lifted that threat, and apparently not even diminished it. If the money and energy devoted to waging war had gone into diplomacy, espionage and policing, it is at least arguable that whoever in Saudi Arabia knew about the Riyadh conspiracy might have stopped it.

What the latest bombs suggest is that the wars changed nothing. They were a sideshow, a diversion of effort, probably choking the intelligence networks that might have kept tabs on the perpetrators of these crimes. The Iraq invasion certainly worsened transatlantic links crucial to monitoring terrorists in Europe and the Mediterranean.

That said, I refuse to be panicked. The Government tried before and during the war to scare the nation witless with weekly threats of imminent chemical and biological attack. The scares evaporated even as the Riyadh bombers were selecting their targets. Yet I cannot claim to feel less safe today than I did, say, 20 years ago. Threats have receded rather than advanced, be they from the Soviet Union, nuclear accidents, the IRA, state-sponsored gangsters such as Carlos the Jackal or such freelancers as Baader, Meinhof and the Red Brigades. We forget how terror-prone Europe was in the 1970s and 1980s.

Today a strand of Muslim fundamentalism is plainly capable of inducing young people to acts of extreme violence. In Saudi Arabia on Monday night the result was devastating. Yet against this threat there is only one realistic defence, from the police and security services. Since September 11 they appear to have been successful. Britain has not been attacked and I take comfort from the fact that most of the suspects closest to September 11 have been seized not by soldiers in war but by police in Western cities.

There will be no let-up in attacks without peace in the Middle East and an American and British withdrawal. That is a truism. But the job of security is not to solve the problems of the world. That is for politics. A policeman cannot end the grievances that foster violence. As Andrew Sinclair graphically remarks in his new book, An Anatomy of Terror, “a little learning is the nipple of the militant, when the mother’s milk is hatred and revenge”. The capacity of the West to generate hatred and revenge in the Middle East is at present extraordinary.

Policing can offer protection only of last resort. It can claim no spectacular victories, only spectacular defeats. As Conrad said, “the terrorist and the policemen come from the same basket” — and they often return to it. Hatred festers in the bedsits of North London as much as in the squatter camps of Arabia. Somewhere in a dirty souk or beneath a railway arch there will always be a maniac ready to pack a car with dynamite and drive it down the road to his — and my — death.

I want that maniac in the souk stopped before, not after, he does me harm. Against him a billion pounds of bomber circling overhead and proclaiming regime change and freedom is no protection. He will be stopped only by another man in that souk, with a radio and a gun. Such protection offers politicians no glamour and contractors no profit. It wins no elections.

I do not care. We have had the razzmatazz of war. Now let us have the reality of protection.