Thirty years ago, every local authority in the country had emergency plans for what to do in case there was a nuclear attack. Many had bomb-proof bunkers for the great and the good.

As the Cold War began to end, these plans were scaled down and for most people, the fear of nuclear bombs has receded.

But the terrorist attack in America, which left more than 6,000 people dead in New York alone, has reactivated fears about public safety.

Then, the threat was usually perceived to be the Soviet Union. Now, it could be any country, or even political group, which has access to nuclear weapons.

There's also the possibility that they would try other form of attack such as chemical warfare.

The most obvious targets can be given some protection, as party conferences have ever since the IRA bomb blast in Brighton 17 years ago. But complete protection to everyone all the time is impossible.

Worried people should console themselves with the fact that the chances of being affected by any attack are small.