An "old guard" of Provisional IRA members recruited by violent dissident republicans are behind what the Army has termed the "growing sophistication" of bombs found in Northern Ireland.
A report for the Northern Ireland Office (NIO) by David Seymour, the independent reviewer of justice and security issues, noted how bomb disposal teams working here are "concerned activity is ramping up".
He also revealed that the devices "with which they have to deal show signs of a growing sophistication."
Sunday Life can reveal this is down to dissident groups like the New IRA and Continuity IRA recruiting into their ranks disaffected former Provos, several of whom have bomb-making capabilities.
In the 12 months until July 2019, the Army's bomb disposal squad was involved in 229 call-outs - an increase from 198 the previous year.
Among the experienced terrorists the New IRA, the most active of dissident republican groups, has recruited into its ranks are Ciaran 'Zack' Smyth, Paul Campbell and Christopher 'Christy' O'Kane.
Smyth had his early release licence suspended in March over his growing links to the New IRA.
A former Provisional IRA prisoner and convicted armed robber, he was suspected by security chiefs of being behind plans to fire a mortar at Musgrave Street PSNI station in Belfast - an allegation he denies.
The 60-year-old is currently listed as a New IRA prisoner in Maghaberry jail, where he shares a segregated Roe House landing with Paul Campbell, a convicted Provisional IRA bomber from Tyrone.
Campbell (41) is serving a reduced two-year sentence for trying to blow up Coalisland RUC station in 1997.
Because the attack took place before the 1998 Good Friday Agreement, he could only be caged for a maximum two years.
Another former Provo bomber at the centre of the New IRA is Christy O'Kane from Derry. The 46-year-old was among a group of dissidents protesting outside Bishop Street courthouse when Paul McIntyre, who is charged with the murder of journalist Lyra McKee, appeared in court earlier this year.
In 2008 O'Kane was sentenced to 10 years in prison after walking into a PSNI station and confessing to involvement in five IRA shootings and bombings that took place between 1993 and 1994.
Because the offences took place before the Good Friday Agreement he only had to serve two years behind bars.
It is republicans like Smyth, Campbell and O'Kane who are adding to what security chiefs have termed the "growing sophistication" of dissident attacks.
Outside of the New IRA, the Continuity IRA is also relying heavily on the expertise of former Provisional IRA members.
This newspaper has previously revealed how Fermanagh-based Continuity IRA chief John Joe McCusker had been seeking help from Omagh bomb suspects Colm Murphy and Seamus Daly.
Both men were found guilty by a civil court of involvement in the 1998 slaughter that claimed the lives of 29 innocent civilians and two unborn twins.
Murphy and Daly had been aligned to the violent Oglaigh na hEireann (ONH) gang which called a ceasefire in 2018. It was after this that McCusker reached out to them for assistance.
Since then the Continuity IRA has re-emerged, trying to kill police in booby-trap bomb attacks in Fermanagh and Lurgan.
Rival dissident faction the New IRA were behind a massive car bomb blast at Bishop Street courthouse in Derry in January 2019, and a device placed under a police officer's car in east Belfast which failed to explode last June.
Backing up security expert David Seymour's dissident 'sophistication' report to the NIO are comments from Chief Constable Simon Byrne.
When a New IRA mortar was discovered aimed at Strabane PSNI station last autumn, he said: "We've seen changing types of engineering and capability that show determination and motivation clearly aimed at killing and maiming officers.
"It (the mortar) was complex, and it was sophisticated, and the threat is clearly changing."
Mr Byrne also confirmed that the mortar may have been built by someone "who had previously been involved in terrorist activity".
MI5, which is tasked with monitoring dissident republican activity, has described the threat posed as "severe" and that future attacks are "highly likely".