The alleged use of an encrypted messaging system led to the arrest of Kinahan gang figure Liam Byrne on Sunday night.
Mr Byrne lives in Dubai along with other members of the Kinahan organisation but flew to Spain for a family meal.
Britain’s National Crime Agency say they were alerted to his presence in Europe after he sent messages on the encrypted EncroChat app and a warrant was issued for Spanish police to arrest him.
“It’s the contention now of the British National Crime Agency that Liam Byrne was on that EncroChat system,” Irish Times Crime Editor Conor Lally said.
“They claim that they have correspondence that was sent back and forwards via EncroChat that implicates him as the leader of a gang that was buying firearms for sale to other organised crime gangs.
“We don’t know whether these messages were actually sent by [Mr] Byrne.”
An Garda Síochána described the arrest as "a particularly significant development'' in international efforts to ''dismantle the operations of the Kinahan Crime Group''.
Mr Lally described Mr Byrne’s trip to Majorca for a family holiday as a “perfect opportunity” for Spanish police to arrest him.
“At this stage, we don’t know what passport he was travelling under,” Mr Lally said.
“But we do know from all of the enquiries that have been carried out - particularly in the last six or seven years since the Regency Hotel attack and the start of the Kinahan-Hutch feud - we know that a lot of these senior criminals… they’re very adept at sourcing fraudulently obtained, legal passports.”
Mr Byrne’s brother, David, was shot dead during the Regency Hotel attack in 2016.
In April, Gerry Hutch was found not guilty of his murder by the Special Court after judges concluded they could not accept the evidence of State-turned witness Jonathan Dowdall.
Jason Bonney and Paul Murphy were sentenced to eight and half and nine years respectively for their roles as getaway drivers after the shooting.
The NCA said Mr Byrne is “thought to be one of he most trusted members of the Kinahan organised crime group” and that he had “evaded justice” for many years.
Mr Byrne continues to be held by Spanish police amid ongoing efforts to extradite him.
Main image: EncroChat. Picture by: Alamy.com