A leading police chief in Northern Ireland has said it is "difficult to see an end" to dissident republican violence.
I interviewed Assistant Chief Constable Drew Harris, head of the PSNI's Crime Operations, as part of a documentary, The New Dissidents.
It would be unwise to overestimate the present threat, but ACC Harris made it clear these republican terror groups are not to be taken lightly.
"It's serious," he told me.
"It still causes the odd sleepless night. It's very difficult to see an end of this."
In particular, what is likely to keep ACC Harris, and MI5, awake is the threat from the new amalgamated group known as the 'New' IRA.
The group was formed last year and is made up of the Real IRA, Republican Action Against Drugs (RAAD) and powerful elements of unaffiliated, hardened former Provisional IRA members from County Armagh and East Tyrone.
He worries about the emergence of a critical mass.
"If that starts as a trend, people may feel it's better to be within this bigger grouping," he added.
"Hitherto they have been very diverse and mistrusting of each other."
I wondered if there was intelligence that other groups were contemplating joining the 'New' IRA?
"We would watch very carefully for that," he said.
"All these groups say to themselves that they are in this for the long run."
His other concern is that a new generation of young people is being attracted to the dissidents and he described the process with words that I have come to associate more with Islamist extremists than Irish republicans.
"Radicalisation is happening," he said.
"Young men, even in their very early 20s, are being charged with serious terrorist offences who must have only been very small children at the time of the Good Friday Agreement.
"They don't have any buy-in to the [peace] process and almost a nihilist response in terms of what a united Ireland would be like. That's worrying."
Northern Ireland Deputy First Minister Martin McGuinness has not pulled his punches in confronting the so-called "dissidents".
There is no doubt about his visceral loathing, having steered the Provisional IRA from "war" to peace and power-sharing at Stormont.
To call the dissidents "traitors to Ireland" with the PSNI's then chief constable, Sir Hugh Orde, standing at his side, was about the most damning insult that he could pay them, many of whom are his former comrades in arms.
Nor was he daunted recently when the PSNI warned him of a serious death threat and his house was daubed with paint.
At last month's Sinn Fein's ard fheis (party conference), he departed from his prepared speech and scathingly asked: "Where were they when there was a war?"
Interviewing Sinn Fein's Gerry Kelly, I got the distinct impression that the party was now rowing back from inflammatory remarks of this kind, perhaps realising that such attacks may be counterproductive. David Cameron is now doing much the same with UKIP.
Mr Kelly was almost emollient.
No mention of "traitors" or republican draft dodgers, although he made his opposition clear in a measured way.
"I think they are wrong," he said.
"I don't think they have an analysis. I don't think they have a strategy.
"But you have to deal with fact, that there are some young people in it.
"They get caught up in the ideology. I can understand where they are coming from.
"What I'm more critical of are the ones who - some of them my former comrades - are almost trying to plot a revolution after it has taken place."
I asked if he had spoken to the dissidents and asked why they were continuing the "armed struggle" when the "war" was over?
"The answer is yes," he added.
"At this moment, the offer is out from myself, and from Gerry Adams and Martin McGuinness, to speak to them about their analysis, our analysis, and where we believe they are going wrong.
"That is a very open door."
It was almost as if Mr Kelly was offering the dissidents an olive branch. Behind the scenes there are signs that some of them may be prepared to take it up.
The problem with the dissidents is that they appear to have no coherent and cohesive political programme.
When all is stripped away, it is "Brits Out" and self determination for the Irish people.
They do not accept that the cross-border referendum, in which there was an almost unanimous vote in favour of the peace agreement, was tantamount to self-determination.
Talking to dissidents today reminded me of talking to the Provisional IRA way back in 1972 when the IRA leadership, that included Martin McGuinness and Gerry Adams, met the Northern Ireland Secretary, William Whitelaw, for negotiations in Chelsea's Cheyne Walk.
The IRA effectively told Mr Whitelaw that if the British wanted peace, they had to withdraw the constitutional guarantee to the unionist majority and leave by 1 January 1975. The British were appalled at the IRA's naivety.
Perhaps the light then gradually dawned on Mr Adams and Mr McGuinness, realising that a simplistic "Brits Out" strategy was going nowhere.
It was three years after Cheyne Walk, that Mr Adams and his comrades in the "cages" of the Long Kesh internment camp began to map out the IRA's long-term strategy that, over two decades later, led to their controversial acceptance of the Good Friday Agreement.
The IRA's acquiescence led to the split in 1997 from which the Real IRA emerged. The following year, they bombed Omagh.
The Real IRA then split into yet more armed dissident groups that are now bombing and killing to try to destabilise the peace process and carry on from where the Provisional IRA left off.
Leading dissident Londonderry republican, Gary Donnelly, places the 'New' IRA in a longer timeframe.
"The Provisional movement didn't appear overnight," he told me.
"It would probably take them (the 'New' IRA) a lot of effort and a lot of time to get up to full steam.
"But the reality is that (as long as) there's a British presence in Ireland, there will always be a respectable minority who will challenge it and who will use force of arms."
However, despite his concerns, ACC Harris does not believe there is any danger of a return to the dark days of the past.
"There's not actually the broad base of support to mount a sustained campaign," he said.
Sinn Fein's Gerry Kelly is even more emphatic.
"It is not gaining momentum because the people do not want it," he added.
"It's as straightforward as that."
Peter Taylor's report on "The New Dissidents" will be broadcast on Tuesday, 7 May at 20:00 BST on BBC Radio Four.