Alleged Kinahan cartel figure Liam Brannigan was moved from Mountjoy Prison when one of his closest mob associates was committed to the jail on serious charges.
The move happened last Wednesday and saw Brannigan (37) transferred to Limerick Prison, away from other cartel members locked up in Mountjoy and Portlaoise.
"Brannigan has been shoving his weight around in recent weeks in Mountjoy," a jail source said last night.
"There was a feeling that if his 34-year-old associate, who got locked up last week, ended up sharing a prison landing with him, they would try and take over the place.
"There has also been underworld speculation that Brannigan is in dispute with some of his associates in the Kinahan cartel and this may have been another reason for the move."
Brannigan, who is a cousin of Regency Hotel gun murder victim David Byrne and a close pal of gangland killer 'Fat' Freddie Thompson, is likely to find himself in an "isolated position" in Limerick Prison, but sources said he was "a disruptive influence" in Mountjoy before his transfer.
"Brannigan would not know too many of the other inmates in Limerick - it will be a strange environment for him," one source said.
"Before he was locked up, Brannigan and the 34-year-old man from the northside who was remanded to jail last week would have been very close to each other.
"Gardai are monitoring the situation to see if there has been a disagreement between the two men or simply that the jail authorities did not want Brannigan and the recently jailed man in the same prison."
Brannigan, from Bride Street in the south inner city, is facing trial with two other men at the non-jury Special Criminal Court in October charged with conspiring to murder Kinahan cartel target Gary Hanley at a location within the State between September 15 and November 6, 2017.
Alan Wilson (39), of New Street Gardens, Dublin 8, and Joseph Kelly (35), of Kilworth Road, Drimnagh, are also charged with conspiring to murder Mr Hanley at a location within the State between the same dates.
Mr Kelly is also facing charges of possessing a Beretta handgun and 15 rounds of ammunition with intent to endanger life at Philipsburgh Avenue, Fairview, Dublin 3, on the same date.
All three have been in custody since being arrested for the alleged murder plot in November 2017.
Another man, Luke Wilson (23), of Cremona Road, Ballyfermot, was jailed for 11 years last November after he pleaded guilty to the same offences at the Special Criminal Court.
Gardai recorded him in "extensive discussions" about the murder plot.
Wilson said in an audio recording that he had "no problem" camping in the back of a van in order "to get" Mr Hanley and that he wanted "money not jail".
He also said: "He [Hanley] doesn't even understand why our people want him gone. He is such a f**king idiot."
A fifth man is also expected to face charges before the court in relation to the same investigation.
Brannigan has been allegedly linked to organised crime over the last two decades, which began with the Crumlin/Drimnagh feud. Before his arrest, he had been studying archaeology at a Dublin university.