In the wake of the failed bombings...

This gesture security is inevitable. But it has barely any practical value

The flurry of precautions after terrorist attacks are almost always charades. Real counter-measures all hinge on intelligence

Max Hastings

Pity anyone who must catch a plane or visit Wimbledon today, or indeed for many days to come. Following Friday's London bombs and Saturday's attack at Glasgow airport, security checks have intensified dramatically. Everybody engaged in what is now a vast industry wants to be seen to be trying harder.

It is another matter, of course, whether all the conspicuous activity that follows a terrorist incident adds a jot to public safety, to compensate for the huge economic cost it imposes. Most security precautions represent a charade. It is probably a politically necessary charade - we will explore that issue in a moment. But we should be sceptical about its practical value.

Gesture security attained its nadir in February five years ago, with the deployment of armoured vehicles at Heathrow. It was possible to accept that the security service and police possessed plausible intelligence that terrorists were preparing to attack an aircraft with a missile. It was impossible, however, to believe light tanks could play a useful part in preventing such an action. Aircraft landing or taking off are within comfortable range of a missile fired from well outside any airport perimeter. Even if an obliging member of al-Qaida knelt with his launcher beside a runway, it is unlikely he could best be frustrated by a 30mm cannon fired from the turret of a Scorpion.

The Heathrow tank deployment was a political, not military, precaution. It was designed to impress the public, rather than in the serious expectation of stopping an atrocity. This was an extreme case of nonsense security, but there are plenty of lesser ones every day in airport search queues.

A dilemma confronts the Home Office, intelligence services and police chiefs every time a terrorist incident takes place. They know that, rationally, there is little chance that imposing car checks at airports will accomplish anything more than adding an hour or two's delay to every passenger's flight time. Yet they are also acutely conscious that if they fail to be seen to raise their game, and another would-be terrorist then crashes into a British airport terminal, it would be a resignation issue.

The usual compromise is that extreme security checks are introduced for some days following a major incident. Then, when the headlines cool and the economic disruption becomes intolerable, security reverts to "normal". This does not represent a logical approach, but it is hard to see any way around it in a democracy vulnerable to media frenzies.

It is also hard for ministers and the police to pitch their public utterances. A reasoned statement, following the weekend's events, might have gone something like this: "After so much speculation about attacks on Britain by terrorists wielding weapons of mass destruction and biological weapons, it is a relief to see these attempts made with weapons as crude as cars filled with petrol and gas cylinders. The group carrying out the attacks are grotesque amateurs. At worst, their efforts might have inflicted the level of fatalities caused by a motorway smash." In reality, of course, it would be unthinkable for anyone in authority to say anything of the sort. Spokesmen must talk gravely about "a threat of dreadful carnage", because anything less would sound flippant and irresponsible.

When a nation is in a state of declared war with a state enemy, the issues are much simpler, and the public soon learns to understand them. When the Germans began bombing British cities in 1940, anti-aircraft guns put up big barrages whenever raiders were overhead. The belief that "we're hitting back" boosted morale. It was soon discovered, however, that shell fragments from the guns were inflicting almost as many casualties as German bombs, and that scarcely any planes were being hit. Most batteries were moved to places where they were less visible but might do some real good. Likewise, people stopped abandoning their work whenever a raid was threatened and sought refuge in shelters only if raiders were close overhead.

Yet conditions and expectations today, in times of peace, are very different. Public safety is threatened only spasmodically, and in the most erratic and unpredictable ways. What the army calls "point defence", meaning the protection of specific buildings and sites against assault, is neither feasible nor credible when the range of possible targets is almost unlimited, and the economic life of the country must continue.

Most of us have become reconciled to the steel gates in Downing Street and concrete barriers outside the Houses of Parliament. These are obviously high-profile targets. There is a real prospect, rendered more vivid by the people who crashed into Glasgow's terminal on Saturday, that terrorists could try to use a vehicle as an assault weapon against Britain's most famous national symbols.

Thereafter, however, common sense decrees that public buildings must take their chances. It is not credible, for instance, to fortify all airport terminals. We should recognise the searching of passengers for what it is, a necessary gesture unlikely to stop a half-sophisticated terrorist from smuggling some instrument of menace on to a flight.

All serious counter-measures hinge on intelligence: identifying potential threats by surveillance and penetration. The security service deserves more sympathy than it usually receives for its difficulties in achieving this. The range of militant young Muslims now in Britain, both homegrown and imported, is frighteningly large.

Since 9/11, MI5 has been deluged in money and has recruited thousands of new officers, including a significant number of Muslims. But it takes years to train such people and enable them to gain the experience to become Smileys. More than that, they do not receive anything like the assistance from the British Muslim community which they need effectively to contain the threat, never mind defeat it.

It is difficult for intelligence officers to distinguish between militants who merely talk big and those actually intending to commit acts of violence. An MI5 officer described to me a while ago the problems posed by suspects who behave normally for months, even years, before suddenly embarking on an attack. Surveillance requires a massive commitment of manpower. Every day, MI5 is obliged to make life-and-death choices about who it will continue to monitor. The quality of police assistance is patchy, to put it politely, and a source of much dismay in intelligence circles.

Although I am as sceptical as many people about the loss of civil liberties in the name of anti-terrorism, it seems essential at the very least to legitimise interception evidence in court proceedings. This is a much more important tool for protecting the public than checking cars approaching airports, and causes far less inconvenience to the innocent.

In the days ahead, we shall see plenty more gesture security, because that is politics in the wake of a terrorist incident. We should recognise it for what it is, however, and not confuse it with measures that serve the real purpose of protecting us from violent fanatics.