Joan Smith: London is not Baghdad or Beirut

It is a strange sensation, living through a day in which the big story is something that didn't happen. Yesterday London wasn't bombed, unlike Najaf, the Shia city in Southern Iraq where 35 people died in a suicide attack on a market and many more were injured. Dead bodies weren't pulled from the ruins of houses in British towns and cities, as they have been daily in Lebanon for the past month. Passenger planes weren't hijacked and flown into buildings, as they were on 9/11, or blown up halfway across the Atlantic.

For this we have to thank Scotland Yard and the intelligence services, which together have apparently disrupted a terrorist plot to destroy several flights - the figure varied from three to 10 in the news bulletins I heard - between London and the US. Overnight arrests led to the UK being placed on its highest state of alert, while unprecedented security at British airports led to flight cancellations and lengthy delays, as well as severe restrictions on what could be taken on board.

According to Scotland Yard, the country has narrowly escaped "mass murder on an unimaginable scale", for which the majority of us are hugely grateful. At the same time, it seems to me that after 9/11, Bali, 7/7 and other worldwide atrocities, the horrible effects of terrorism are all too easily imaginable. Listening to the BBC yesterday, with much of the Today programme given over to the foiled plot and an extended edition of the World At One, it was almost possible to believe that another attack on the scale of 7/7 or worse had already happened.

Because there were no survivors to speak to, bulletins were fleshed out with interviews with stranded travellers. Being stuck at an airport is hardly a riveting experience, and the first-hand experience of passengers merely served as a reminder that air travel is likely to become ever more frustrating as would-be bombers think of new ways to get around airline security precautions. I assume that terrorists are, in this respect, much like car thieves, who have reacted to the installation of ever more sophisticated anti-theft devices by waiting for drivers to appear and making them hand over the keys at knifepoint.

Much of what was reported was speculation, perhaps informed by off-the-record briefings, but facts were hard to come by. This is not to say I subscribe to the view that because Scotland Yard apparently made the wrong call when they raided a house in Forest Gate, everything they say about terrorist threats should be taken with a pinch of salt. We have all read accounts of the carnage and human suffering caused by the 7/7 bombers, who turned parts of London in the rush hour into something resembling a war zone.

After those attacks, some of my friends found it hard to continue using the underground, adopting new and inconvenient routes to work because they couldn't bring themselves to get on a Tube. Like many Londoners, I carried on as usual, aware that the odds of being injured in a terrorist attack in this country are still pretty low. That's still the case, despite what we discovered yesterday, but I worry about the effect of the latest revelations on our sense of proportion.

Ever since the grim aftermath of the invasion of Iraq, we have lived with dire warnings about the inevitability of terrorist atrocities. I take these seriously, not least because I have twice found myself close to terrorist attacks, in Istanbul in 1994 and Soho in 1999. On the latter occasion, I was in a bar, close to the gay pub where a nail-bomber left a homemade device, and I not only heard the explosion but saw the dreadful aftermath of the blast in Old Compton Street.

I'm also aware, however, that most of us still enjoy the luxury of going about our business without the likelihood of being killed or injured by a bomb. London isn't Baghdad or Beirut, nor are we likely to see death and destruction on anything like the scale being experienced in those two cities. Last year, to be precise, 52 people (and four bombers) died in terrorist attacks in London, a terrible tragedy for families and friends.

In the same period, according to the Government's own figures, 3,201 were killed on British roads, slightly more than the total casualties on the east coast of the US on 9/11. Another 28,954 people were seriously injured, making the car journey to work a much more risky proposition than using the Piccadilly line. In fact, between 1951 and 2003, a staggering 299,601 people died in road traffic accidents in this country and another 16 million were injured. These are mind-boggling figures, but because we don't wake up each morning to a detailed news report from the scene of each fatal accident, we manage to put the risk out of our minds.

The Government quite rightly comes up with measures to bring down the number of road deaths, but we have yet to see the Transport Secretary of the day making speeches - as the Home Secretary, John Reid, did yesterday - warning that the threat is so great that we have to give up our historic liberties to save lives. There is even a vocal lobby against speed cameras, as though in excess of 3,000 fatalities each year is a reasonable price to pay for the right to exceed the speed limit in built-up areas.

Logically, the threat from terrorism ranks somewhere below that from cars and lorries, and well below the effects of global warning. Unfortunately, it's more newsworthy and a lot more exciting, with even a foiled terrorist attack in which nobody dies creating an atmosphere of urgency that's never going to be prompted by a motorway pile-up. Politicians, police officers and reporters all read from the same script on such occasions, never stopping to ask about the consequences of impressing upon us the idea that we're five minutes from catastrophe.

Fear warps judgement and encourages overreaction, as we can see from the Israeli government's massive response to the rockets of Hizbollah. Unless I am wildly mistaken, home-grown terrorists have the capacity to commit occasional spectacular atrocities in this country, but we are not talking about an invading army or an enemy with the capacity to inflict air strikes.

This is an unpleasant fact, whose causes we can and should debate, but it's not a reason for panic. There was no terrorist attack on the UK yesterday, a situation most Iraqis would be immensely grateful to find themselves in. And with such ghastly news from the Middle East each day, isn't it a bit distasteful to get so worked up about a sequence of events which resulted in nothing worse than disruption at British airports? I have yet to be convinced that our way of life is under threat, although new restrictions on hand baggage mean I'm less sanguine about our duty-frees.