The alleged Number 2 in the Kinahan crime cartel and his son were arrested by Britain's National Crime Agency yesterday in a major operation involving the Garda Siochana and other agencies fighting organised crime in Europe.
The arrest of the 51-year-old is being seen as a major breakthrough in the fight against the cartel.
He has lived a luxury lifestyle in Britain for the past nine years and is a frequent traveller between the UK, the Middle East and Spain.
Police said he is being held on suspicion of importing and supplying drugs and weapons and laundering cash.
His son, who is aged 20, was also held on suspicion of money laundering after a precision swoop as both men arrived at Birmingham Airport yesterday morning on a flight from outside the EU.
He has since been released on police bail.
The operation involved a number of international agencies, including the Garda, and was continuing last night as police in the UK carried out a detailed search of a gated detached home in Tamworth, a market town 14 miles outside of Birmingham. The house is in Tamworth's most exclusive area and is the locale of a number of celebrities and professional footballers.
The 51-year-old, who is regarded as second-in-command in the Kinahan gang, is well known to gardai and has convictions in this jurisdiction for assault, threats to kill, possession of firearms and assaults on gardai. He has been a target of the Criminal Assets Bureau in the past and left Ireland in 2008.
The arrests are part of a major probe into organised crime, international money laundering and the supply of narcotics and weapons.
The National Crime Agency (NCA), which specialises in organised crime in Britain, spearheaded the operation which focused on the supply of drugs and firearms into the UK and Ireland. In a statement the NCA said that two men had been arrested as part of their investigation.
"A 51-year-old man was arrested on suspicion of conspiring to import and supply drugs, firearms and ammunition, as well as money laundering offences on arrival at Birmingham Airport yesterday. At the same location a second man, aged 20, was arrested on suspicion of money laundering offences."
NCA officers also searched a property in a business premises in Birmingham.
Assistant Garda Commissioner John O'Driscoll confirmed gardai assisted, saying: "We share a common desire to put organised crime groups who operate in the common travel area out of business."
The assistant commissioner said: "For the purpose of tackling organised crime groups, An Garda Siochana has commenced the new year in the manner in which it intends to proceed in 2019, by engaging in the most impactful possible co-operation with law enforcement authorities, at an international level.
"In this regard the UK National Crime Agency is one of our most important allies, with whom we share a common desire to put organised crime groups who operate within the common travel area out of business.
"An Garda Siochana will not make any comment regarding any particular operation which is currently ongoing," he said.