TONY Blair's words could not have been more sombre, nor his assessment of the world order more grim.

His Mansion House speech left no doubt: Britain is an explicit terrorist target. New threats to our national interests land on the Prime Ministerial desk daily. And some are being treated with the greatest seriousness: witness our ferry ports being placed on high alert.

Suddenly, it is hard to recall the halcyon days when the world seemed to be entering a more peaceful era. When the Second World War gave way to the Cold War, it seemed mutual distrust could lead to mutual destruction. Those shadows lifted with the fall of the Berlin Wall. For a moment it seemed that man's capacity for tolerance was dominating our desire for aggression.

September 11 shattered that fond illusion. Soviet communism had been replaced with a new danger: fanaticism.

In the Cold War we had a known and unmoving enemy. In the war against terrorism, there are no certainties. The targets are as haphazard as they are deadly: a New York office block, a Russian theatre, a Bali nightclub.

That makes it so much more difficult for the authorities, national or local, to draw up contingency plans. As Mr Blair put it, "the dilemma is reconciling warning people with alarming them; taking preventive measures without destroying normal life".

He is right to be up front with the British people about the perils we face. The risk of scaring people unnecessarily is outweighed by the need to keep us informed.

One of our most defined national characteristics is stoicism. We met the horrors of two world wars and an IRA bombing campaign with an unflappable determination to carry on: we will face this threat just the same.

What we do need is more information. It is very well for the Government asks us to be vigilant, but we need to know what we are looking for. Mr Blair has come clean about the threat; he should now tell us what we can do about it.

Updated: 11:52 Tuesday, November 12, 2002