The tragic events that we have seen in the last few days in Northern Ireland are something that many on this side of the Irish Sea had thought were in the past.
This sort of callous and brutal murdering of soldiers and a serving police officer has not been witnessed there for more than a decade.
I can not pretend, however, that for me these atrocities have come out of the blue. It has been well known for the past eighteen months or so that the threat from dissident republicans has been steadily increasing. The Chief Constable of the Police Service of Northern Ireland has been quietly but firmly warning us that attacks of this sort were not just possible but likely.
The most recent report from the Independent Monitoring Commission warned that dissidents had been especially active and that they had turned their efforts more directly to trying to kill police officers.
It reported also that the Continuity IRA not only undertook direct attacks but also engineered public disorder with a view to exploiting the exposure of police officers which they expected to result from it.
For politicians on the UK mainland and in Northern Ireland the priority now must be to respond in a way that strengthens the political process.
Change to the way that policing is carried out has been one of the most visible benefits of that political process.
Forcing police into barracks and armoured vehicles and away from the communities they serve is exactly what the terrorists want to see. Allowing it to happen is to hand them a victory.
The safety of serving police officers cannot, however, be compromised. The answer, as the First and Deputy First Ministers made clear, lies with the people of Northern Ireland themselves.
If they want to maintain what we in the rest of the UK regard as normal policing then they must cooperate with the police in dealing with this attack on it. Harbouring murderers is the best way to return Northern Ireland to the dark days of the past
For government in London too these tragedies must act as a wake-up call. Treasury demands for economies in the policing budget were misplaced. The cost of meeting Northern Ireland’s policing needs may be large. The cost of under-funding them could be enormous.
The construction of a shared future by peaceful and democratic means is, to paraphrase the late John Smith, the settled will of the people of Northern Ireland. Political leadership is now needed to resist a bloody challenge to that. Politicians with the courage to lead will, I believe, find a community keen to follow.
Alistair Carmichael is Lib Dem spokesman on Northern Ireland