In that dissident republican world the Continuity IRA was there before the so-called Real IRA.

The history of this organisation probably dates back to the 1980s, and its roots are in the fallout within Sinn Fein over a decision to enter the Dail if elected, in other words to end the policy of abstention.

Then, Ruairi O Bradaigh led the walkout, and while Republican Sinn Fein does not present itself as the political wing of the Continuity IRA, the two are seen as closely linked or associated.

In its violent form it took until July 1996 for CIRA to emerge, carrying out a bomb attack in Fermanagh in the heat of that year’s marching season.

“Why didn’t they fight the Brits from ’86 to ’96?” one republican asked. “People who fought the Brits would look down their noses at them.”

Now, the Continuity IRA has put its name to murder, to the killing of a police officer in Craigavon.

In the confusion of that dissident world it will take some time to authenticate or dismiss that claim.

The Continuity and Real IRAs are separate groups but republicans and the security forces believe they co-operate.

And, not long ago, the Chief Constable Sir Hugh Orde talked of a “competition” among the dissidents to see who would be first to kill a police officer.

That has been their deadly game — the focus of these groups stretching back over 18 months or so.

The Real IRA has admitted the killings at Massereene Barracks, and now the Continuity IRA claims the Craigavon murder.

Police will take their time before coming to any firm conclusions of their own.

It is difficult to be certain about anything that happens or is claimed in that dissident world. It is fractured, disparate, confused, and even within the splinter Real and Continuity IRAs there are splits.

The intelligence assessment is that the bulk of their leaderships are based across the border. But it is here in Northern Ireland that there is a very specific security focus at present.

How, after months and years of failure, have these splinter republican groups managed to carry out the killings of recent days? How did they get in under the radar?

In all of the assessments that are going on at present those are just two of the questions, and part of the investigation will also be a close examination of the claims that have emerged since the weekend.

Who is masterminding the killing? Who is doing their dirty work? And why are these attacks taking place now?