Leading article: The unionists must respond to this historic announcement

That is, of course, to be welcomed. But it would quite unjustified to praise the IRA for making this commitment. It should never be forgotten that hundreds of innocent people have been killed by the IRA's bombing campaigns over the past 30 years, both in Northern Ireland and Britain. The IRA is wrong to argue that "the armed struggle was entirely legitimate". Acts of terror against civilians can never be acceptable, and the IRA should not have adopted such methods in the first place.

The onus is now on the IRA to prove that it is as good as its word. Yesterday the order went out to "dump arms". In the past this has meant putting weapons out of action by hiding them in scattered stockpiles. This time it must be different. All guns, explosives and bullets must be permanently destroyed and the decommissioning process independently witnessed. Nor is it not enough for the IRA to simply cease all "military" activities. The punishment beatings, the robberies and all forms of criminality in which the IRA has long been engaged should be brought to an end too.

But there is also an onus on the unionist movement, in particular the Democratic Unionist Party leader Ian Paisley, to respond to this significant gesture. Every effort ought to be made to restore devolved government to Northern Ireland. And criminality is by no means limited to the nationalist areas. It is just as incumbent on loyalists to stamp out the thuggery and low-level violence that exist in their communities.

There is a healthy scepticism about "breakthroughs" in the Northern Ireland peace process. But there are grounds for more optimism than usual on this occasion. The reason is that the IRA's statement does not have any conditions attached. Having pledged to decommission their arms, they are now bound to do so. They can no longer blame anyone else - whether Mr Paisley or the British government - if it does not happen. The IRA is likely to have done a deal with Tony Blair to begin the dismantling of army watchtowers and allow the return of various fugitives. And this, no doubt, explains the release of the Shankill road bomber, Sean Kelly, this week. But none of this is part of an official agreement. That means the process of disarming the IRA has a momentum it previously lacked. It will also now prove more difficult for Ian Paisley to refuse to enter devolved government with Sinn Fein. Mr Paisley has always maintained that he will not do business with terrorists. If the IRA decommissions its weapons, this stance is arguably no longer relevant.

The Good Friday Agreement, which paved the way to yesterday's announcement, looks likely to be one of Tony Blair's outstanding achievements as Prime Minister (although the role of his predecessor, John Major, should not be forgotten). But the irony of the contrast between this historic new era in Northern Ireland and the new terrorist danger in Britain is stark.

However, there are lessons to be learned from the Northern Ireland experience in how we respond to the threat from Islamist fanatics. A heavy-handed policy of internment, not to mention several high-profile miscarriages of justice, proved deeply counterproductive in efforts to defeat terrorism in the past. The Government and the legal establishment must be scrupulously careful to avoid repeating these same mistakes.