Gangland boss Wayne Dundon is back on 23-hour lockdown after prison staff carried out a raid on his cell.
He is in a segregated cell in Mountjoy where he is now subjected to regular searches and a strict regime.
Dundon, who is serving a life sentence for the murder of innocent businessman Roy Collins, has been left furious over the move.
An "Aladdin's cave" of contraband was recovered by a specialist search team attached to the Operational Support Group after they raided his cell in the B Basement.
Body cameras, recording devices, hacksaws, steroids, epi-pens and an Amazon fire stick were among some of the valuable prohibited items recovered.
As a result Dundon, along with his younger brother Dessie (34), were moved back to the prison's Challenging Behaviour Unit (CBU) in the C Basement.
After being moved back to solitary confinement it means they will only be allowed out of their cells one hour every day, and have limited access to other inmates.
They will also be restricted to a single weekly prison visit.
A source told the Irish Independent: "The Dundons' influence in the prison has been growing after Wayne was first moved out of the CBU.
"He had been trying to get to a less restricted regime since being transferred, but it didn't last long and he's back on 23-hour lockdown," the source said.
Wayne Dundon was first moved to Mountjoy in 2017 after racking up a substantial list of sanctions in Portlaoise Prison for possession of contraband.
One raid that year, also carried out by OSG, resulted in a large range of electronic devices and weapons being found in their cell.
Mobile smart phones, SIM cards, Stanley blades, Google chrome casts, syringes and steroids were seized during that operation in May 2017.
When officers searched Dundon's cell, he deliberately defecated on himself in a bid to hide the contraband.