Jailed ex-INLA gunman Frankie 'Studs' Lanigan was involved in nine murders on both sides of the Irish Sea.
The hitman for hire's victims include three leading loyalists and a west Belfast drug dealer who he killed for the IRA, sources have revealed.
Across the water Lanigan (56) is the main suspect in the unsolved murder of a Belfast-born car dealer in Manchester.
He also shot and wounded exiled IRA double-agent Martin McGartland at his home in Whitley Bay, Northumberland.
Lanigan, sentenced to a minimum 20 years in prison earlier this month for the 1998 murder of Lisburn-based John Knocker, is believed to have gunned down Pat Logan in Manchester the following year - one of the nine killings in which he was involved.
At the time Lanigan was on the run in Dublin from police in Northern Ireland and living under the alias Ciaran McCrory. But that did not prevent the former semi-professional kickboxer, who sources say was working as an assassin for hire, travelling to England to carry out shootings.
INLA insiders told Sunday Life that he sailed across the Irish Sea twice in 1999 to murder Logan, and seriously wound in-hiding IRA informant McGartland, who survived being blasted six times.
Lanigan has previously admitted being asked by the Provos to kill double-agent McGartland who infiltrated the organisation in west Belfast, but turned down the request.
A month after the McGartland murder bid, Logan was gunned down at his home in Manchester. He was shot five times while making a frantic 999 call to report intruders in his home.
Republican sources say the 40-year-old was targeted by Lanigan over his links to the March 1998 murder of major Belfast drug dealer Brendan 'Bap' Campbell, which was claimed by IRA front group Direct Action Against Drugs (DAAD).
Lanigan carried out the killing for the Provos because Sinn Fein was at the time involved in political talks that would lead to the signing of the Good Friday Agreement weeks later.
"The IRA used Frankie to murder Bap Campbell so there would be no political repercussions for Sinn Fein," said an INLA veteran who was once close to Lanigan.
"Pat Logan provided Frankie with the gun via a Manchester crime gang, but he didn't know what it was going to be used for. He ended up getting really paranoid and thought he would be arrested for the Bap Campbell murder and Frankie found out about this.
"That signed Logan's death warrant. Frankie was worried that he would squeal on him to the cops so murdered him to prevent that happening."
Detectives in Manchester have publicly claimed the Logan murder may have been carried out by a hitman, with his links to Northern Ireland at the centre of their investigation.
In the family's most recent public appeal for information, the murder victim's brother Frank said that it feels like they have been forgotten.
He added: "I'm sure my brother must be turning in his grave that his killer is still out there. When Patrick was killed it broke our family apart.
"We have never had closure - it's like he's just been forgotten. I think someone in Manchester knows something and I want them to come forward."
Lanigan was one of Northern Ireland's most prolific paramilitary killers during the 1990s, and has been linked by several well-placed republican sources to at least nine murders.
These include those of Samuel Rock, Jack Murphy and Jack Smyth who were shot dead by the INLA between 1993 and 1994.
At the time Lanigan was vying with the organisation's future leader Gino Gallagher to be the gang's main gunman. In June 1994, both played prominent roles in the INLA drive-by killings of leading loyalists Trevor King, Colin 'Crazy' Craig and David Hamilton on the Shankill Road.
The trio were gunned down by Gino Gallagher who escaped with two other republicans in a stolen car onto the nearby nationalist Falls Road.
Lanigan spent weeks planning the murders by going on regular morning jogs along the Shankill past the scene of the attack. Our source added: "Frankie was ruthless, make no mistake about it, and he was clever with it too - if you crossed him he'd come back for you."
INLA leader Gino Gallagher was to learn that to his cost when Lanigan set him up to be murdered by drug dealer Kevin McAlorum at a social security office in west Belfast.
He signed on the dole around the same time as his rival, information which he shared with his killer.
Lanigan was desperate for revenge on Gallagher who had ordered his kneecapping and expulsion from the INLA the previous year. The murder sparked a bitter internal feud that cost five more lives including that of eight-year-old Barbara McAlorum, the younger sister of Kevin McAlorum.
In 2004 McAlorum was shot dead after dropping his child off at a school on the outskirts of west Belfast.
Frankie Lanigan was arrested last year in connection with the killing while on remand at Maghaberry Prison, but freed without charge after denying involvement.
In statements to Irish detectives while fighting extradition to Northern Ireland to face charges of murdering John Knocker, he admitted meeting McAlorum in Dublin two weeks before the fatal shooting.
Relatives of McAlorum accuse Lanigan of murdering him - something he rejected in letters to Sunday Life written from his jail cell, saying: "I loved Kevin, he was a special friend."
However, republican sources have rubbished this denial and insisted Lanigan was the gunman.
"Frankie murdered McAlorum to get back into the INLA's good books, saying he had avenged Gino's death even though he set Gino up to be shot dead," explained an insider.
"He also thought it would please the Provos because McAlorum was a big drug dealer. That's the reason why Frankie got involved in the attempt to kill Martin McGartland, it was a favour to the Provos who had set him up with a new life and identity in Dublin as a reward for shooting Bap Campbell."
Lanigan's past finally caught up with him in 2013 when his new life as Dublin barber Ciaran McCrory came crashing down following his arrest for the murder of John Knocker outside a Dungannon nightclub.
He was extradited back to Northern Ireland in 2018 and two weeks ago was sentenced to life with a minimum 20-year term for the killing.
Lanigan shot the 22-year-old west Belfast man twice because he got the better of him in a fistfight.
What has puzzled republicans is how he was able to spend 15 years on the run in the south while working as a hitman, especially after relatives of Kevin McAlorum publicly revealed his Dublin whereabouts years before his arrest. An INLA source told this newspaper: "Either the cops were sloppy or Frankie was being protected. People can make up their own minds."