That a terrorist attack can be known simply by the American abbreviation of the date says much about the scale of the tragedy that occurred on that day.

Nobody could possibly make light of the horror that took place.

Nor could anyone deny that the atrocity changed the rules forever: when terrorists are prepared to sacrifice their own lives in order to murder others, the task of trying to prevent such attacks becomes immeasurably more difficult.

But there is one simple truth that the world's governments seem to have completely forgotten. The aim of terrorism is to terrorise. Terrorists don't succeed when they blow things up or kill people: they succeed when they frighten us into changing the values by which we live.

America has done that, not merely trampling on its own Constitution in its treatment of alleged terrorists, but tearing it up and stomping the pieces into the mud. What greater victory could Al-Qaeda have hoped for than to see a nation which once prided itself on the concepts of freedom and justice set aside those values so readily?

Americans seemed oblivious to the sad irony of allowing fear of terrorism to lead to it closing to the public the nation's most potent symbol: the Statue of Liberty.

One must perhaps make allowances for the US reaction. Aside from the Oklahoma City bombing, the US had scarcely known the concept of terrorism. It had no experience of defeating terrorism by essentially ignoring it: sending the message to terrorists that nothing they do can change the way we live our lives.

But Britain has no such excuse. We lived through decades of IRA terrorism, steadfastly going about our normal lives throughout that time. So it is particularly disappointing to witness in Britain the same type of hysteria we have seen sweep the USA.

At airport security checkpoints, passengers are not permitted to take on board keyring-sized corkscrews. Photographers taking photos of tourist attractions have found themselves detained by armed police. The Palace of Westminster is surrounded by ugly blocks of concrete as supposed protection against car-bombs.

We could perhaps justify it if there was the slightest benefit to any of this nonsense. But the truth is that it is all spectacularly pointless. Let's examine the three examples I've just given ...

The terrorist at the airport who has just had his keyring confiscated can walk 10 metres past Security and straight into the Duty Free shop where he can purchase a large glass bottle filled with flammable liquid. Smash the bottle in half and he has a far more vicious weapon than any pen-knife.

A terrorist on a reconnaisance mission would not be walking around with a bloody great SLR round his neck, drawing attention to himself. He'd be using a camera-phone to take photos while apparently chatting away or sending a text.

And a terrorist looking to attack Parliament can simply walk into the lobby with a briefcase bomb, getting further into the building than any car-bomber could have done even before the silly concrete blocks were erected.

Yes, the rules have changed. Yes, the type of deterrence measures that worked against terrorists who wanted to walk away afterwards will have no effect on those prepared to die. But let's be honest about this: there is not the slightest possibility of preventing suicide bombings.

The tube bombings demonstrated this. Unless we are going to reduce the capacity of the tube network by about 95% in order to screen passengers, there is simply no way to prevent another tube bombing. The same thing at Heathrow: the passenger volumes make it utterly impractical to install xray machines at entrances the way some very quiet airports do. If someone wants to explode a suitcase bomb in the middle of the check-in area, there is not a thing we can do to stop them. The few gaps we can close (such as the screening being introduced on the Heathrow Express) just means that terrorists will choose alternative targets.

We are spending millions of pounds on pointless posturing, and the only thing we are achieving is causing massive inconvenience to ordinary members of the public.

At airports, it's not unusual these days to go through one security screen as you go airside and a second one as you enter the gate. In the old days, it wasn't a big deal. Remove the big items from your pockets, stick your bag into the machine and walk through the metal detector. But these days it can involve removing every last coin from your pocket, taking off your belt, removing your shoes and having your laptop removed from the case and put through the machine a second time, sometimes then being put into a separate explosives-sniffer afterwards. It's reached the point where at peak times you have to allow 30-40 minutes just to get through Security.

We have tubes, trains, shops and streets closed by abandoned McDonalds bags. We have armed police patrolling train stations. We have whole gangs of police searching little old ladies' handbags in tube stations in a vain attempt to pretend not to be targeting Arabic-looking men with backpacks. We have security guards rushing out of buildings to accost architectural photographers. It's absurd and useless.

We are introducing identity cards, aka a permit to be at large. The 9/11 terrorists were all in the country legally, and all would have carried identity cards. The tube bombers likewise. It's a stupidly expensive exercise in bureaucratic futility.

It could be argued that the restrictions and inconveniences we face are trivial. That it only affects the little things in life. But everyday life comprises the little things. And dozens of petty, ineffectual restrictions on our ability to go about our business add up. Worse, each one enables terrorists to look with satisfaction at what they have achieved, at how much disruption and annoyance they have succeeded in creating.

We will not prevent terrorism by security measures. We will end it by demonstrating that it will achieve absolutely nothing. Not even adding a minute's delay to our day. It's time we did just that.