A former head of the Metropolitan Police anti-terrorist squad has said dissident republicans “cannot win” and that their activities will “never” bring the Army back onto the streets of Northern Ireland.

John Grieve — now one of the four IMC commissioners — was speaking after the publication of its latest report.

It pointed to the highest levels of dissident activity since the monitoring commission began its work six years ago — and reported that some former mainstream republicans were now helping groups such as the Continuity and Real IRAs.

Speaking in a Belfast Telegraph interview, Mr Grieve gave this assessment of the dissident threat: “It’s a series of fragmented groups, not very many people coming together — sometimes on an ad hoc basis, sometimes as part of an overall grouping.

“They are particularly active at the moment. The murders took place (at Massereene Barracks and in Craigavon), the sheer number of improvised explosive devices, some of which are more sophisticated than others, some of which are very old-fashioned.

“It’s about the volume of shootings there is in that community and it’s a sense that there is an event every couple of days,” he said.

He described the threat as “severe”.

“It’s very dangerous but it is set within a context that there’s no resemblance to the past,” he said, meaning the dissidents do not pose the same threat that the mainstream IRA once did.

“I think it was summed up by the former Chief Constable — that they are trying to make themselves relevant,” Mr Grieve added.

“They have no chance of unravelling the peace process.

“All they can do is to get themselves headlines and to try to challenge the peace process and to undermine things like community-based policing.

“They’re never going to get the Army back — that is just not going to happen.”

None of what he said was meant to downplay the dissident threat.

The latest IMC assessment points to a situation that is getting worse in terms of the seriousness, range and tempo of dissident attacks.

But the former senior Metropolitan Police officer knows that the mainstream IRA, with bunkers packed with Libyan weapons, could not achieve a military victory.

And on the dissidents, Mr Grieve said: “I am absolutely convinced they cannot win.”