An uneasy fear has gripped Britain ever since the horrific events of September 11.

Over and over again we watched those terrible images of two planes crashing into the Twin Towers in New York. Amidst our sympathy for the victims, we began to wonder, what if it happens again? What if it happens here? To me?

As the conflict escalated, the feeling of dread increased. And then came the anthrax scares -- both genuine and hoax -- which brought us nightmare-like pictures of emergency workers in spacesuits and plunged the nation into terror.

Some people have been rushing to buy gas masks and protective suits, regardless of what good they could actually do. Others are too afraid to set foot on a plane in case it is hijacked by terrorists. Many have a chilling feeling that the end of the world is nigh.

In addition, more prosaic fears about the economy abound. Gloomy financial forecasts, in the wake of the terrorist attacks, have made many of us feel that our jobs and livelihood at the very least are threatened.

But is this widespread feeling of anxiety a normal or rational response to the troubles around us? After all, in Britain at least, nothing bad has actually happened yet.

The anthrax at the Liverpool post office turned out to be sand. Those who were decontaminated at the Stock Exchange received the all-clear. The white powder which caused alarm at a Middlesbrough sorting office was found to be crumbled indigestion tablets.

Robert Edelmann, an honorary professor of psychology at the University of Surrey and author of a book called Anxiety: Research and Treatment in Clinical and Health Psychology, believes our reactions are understandable.

"When nothing happens it is more fearful than when it does," he says. "If we look back to normal warfare during the Second World War, there were an awful lot of people exposed to bombs and having to go to air-raid shelters and very few of them developed clinical fears. That has been documented in lots of studies after that war.

"It is the fear of the unknown that is often more threatening than the fear of things you have to confront and deal with."

Edelmann says our current terror is triggered by the possibility that we are all at risk and, crucially, we have no control over the situation -- an attack could happen to anyone, anywhere and there is nothing we can do to prevent it.

He says: "If it was conventional warfare, we would have a warning, even if it was only a few seconds beforehand. With this situation, we just don't know."

Ronald Bracey, a clinical psychologist in West Sussex specialising in social anxiety, says our fears are also probably heightened by the "popular consciousness" of end of the world predictions.

Whether we believe the doom-mongers or not, he points out that we all know about the Biblical predictions of the apocalypse and the dire warnings of ancient forecasters and, on some level, they could be playing on our minds just as they did at the Millennium.

However, Bracey says many people are making matters worse by "catastrophising" the situation.

He explains: "This means taking an event and kind of maximising the worst possible outcome you could imagine.

"So people will stop going on holiday in case terrorists are on the plane despite the fact that hundreds of thousands of flights are happening every day and the chances of it occurring again are very small.

"In their minds, people alter the odds on things like that happening to them. Odds that are millions to one become ten to one because of people's feelings about it."

The psychologist believes, though, that some people will cope with the situation better than others. Those who have practical and common-sense views of the world, he states, are most likely to say the chances of suffering a terrorist attack are remote.

By comparison, those who are more prone to worrying -- and particularly the 10 per cent of the population who suffer from phobias or social anxiety -- are most likely to let the atmosphere of malaise affect them.

"In the middle," he says, "I think we have got people who are reminded of things like mortality which doesn't really come into our thinking very often."

Bracey says people can take measures to reduce the fear they feel. "Some people cope by just denying reality. They just don't accept it. They don't watch the news or listen to it or take an interest." But this head in the sand approach, he admits, is not really practical in today's world.

A better strategy might be "decatastrophising" the situation by taking a realistic look at the tiny chances of suffering an anthrax attack or being in a hijacked plane and getting things into perspective.

"People are more likely to be having problems with their cardiovascular system and other illnesses than being victims of terrorist attacks," Bracey says firmly.

Edelmann offers similar advice, stating that most feelings of fear and paranoia are caused by the negative internal dialogue people have inside their own heads.

He says this can potentially be turned around by thinking: "What is the likelihood of this happening? Is this really a way forward? Is there any point in disrupting my life? I need to get on as normal."

But at the same time, Edelmann says we must stay vigilant. After all, the fears we are experiencing are not completely groundless.