Jackson was mentioned in the report as being one of those named by former RUC officer John Weir as being involved in planning the bombings.
Christened 'the Jackal' by an imaginative journalist, Jackson is believed to have carried out his first killing in 1973.
The former member of the UDR was linked to the murder of Banbridge trade unionist Patrick Campbell in October of that year, although charges were later dropped.
Jackson was linked to more than 50 more killings before his death from cancer in June 1998, but was never again charged with murder.
There were persistent claims that Jackson had connections with military intelligence and thus had virtual immunity from prosecution.
Republicans have alleged he was actually provided with weapons and information to carry out many of the sectarian killings.
In 1993 journalist Paul Foot claimed in satirical magazine Private Eye that Jackson had been in charge of the Dublin bombings and "has continued murdering people ever since, to the profound indifference of the authorities".
Jackson was named as the gunman in the 1977 so-called 'Good Samaritan killing' of William Strathearn, a Catholic shopkeeper who was shot after he went to the aid of late night callers claiming to need medicine for a sick child.
Two policemen were convicted of the murder and one of them named Jackson as the gunman.
When asked by the judge why he had not been brought before the court, the officer referred to "reasons of operational strategy".
He served just one jail term three years for possessing guns.
Hanna, who was also identified by John Weir as planning the bombings, was a well-known member of the UVF and had been identified as the leader of the organisation in Portadown, Co Armagh. He also had a long military record receiving an award for gallantry for his service in Korea including two years as a member of the UDR, where he was promoted to sergeant and made an instructor.
It had been claimed that Hanna had been used as an agent by British military intelligence agents. He was shot dead in his car as he arrived at his Lurgan home in July 1975.
While no group claimed responsibility for the murder, it was commonly believed he was killed by the UVF following an internal dispute.
It had been claimed that Hanna was shot dead by his former ally Jackson in an attempt by the latter to take over a cache of weapons.
Known as 'Frenchie', Marchant is said in the report to "almost certainly" be the UVF 'officer' named by journalist Robert Fisk as being overall UVF 'commander' and interned by Merlyn Rees, partly on suspicion of having planned "the Irish bombings".
Marchant was shot dead on the Shankill Road by the IRA while standing outside the PUP offices in 1987.
Young was said by former RUC officer John Weir to have admitted his involvement in the Monaghan bombing to him.
Payne is noted by the inquiry as having been a key figure in the Belfast UDA and named by John Weir as having been involved in the Dublin operation.
He was a former north Belfast UDA 'brigadier' and was one of the most senior loyalists during the troubles and died as a result of heart problems earlier this year.
He was questioned over the brutal murder of SDLP senator Paddy Wilson and Protestant friend Irene Andrews who were killed by UDA men in June 1973.
The pair were shot and then stabbed to death in what a judge later described as "a frenzied attack, a psychotic outburst". Then UDA leader John White was sentenced to life imprisonment in 1977 for the killings.
Payne was one of the first loyalists to be interned in the early 1970s at the height of one of the bloodiest periods of the troubles.
In 1978, he escaped a loyalist murder bid after a fall-out with a UDA leader in west Belfast.
In 1987 the UDA brigadier came to prominence after he was arrested in a convoy of cars in Portadown. When searched, two of the vehicles were found to contain 61 AK47 assault rifles, 30 hand guns, 150 grenades and 11,500 rounds of ammunition.
Payne, who had been driving a scout car for the two vehicles, denied any involvement but a personal organiser was found to contain the home numbers of the two other drivers.
Fibres from Payne's clothing were also found on the weapons and his name had been used as a reference for hiring the cars.
It later transpired that the weapons were the UDA's share of a huge consignment of arms smuggled into Northern Ireland from South Africa.
Payne was sentenced to 19 years in jail for his part in the weapons smuggling.
The report says of Ronald 'Nikko' Jackson: "In June 1974 (he) was described by gardai as a UDA major and military commander of a UDA splinter group in the Portadown area. In December 1975, he was said to be a member of the UVF. According to RUC and UVF sources with whom the inquiry has spoken, Nikko Jackson was not a member of either group but was employed by both for his skill in car-stealing and bomb-making".
Identified in the report as having been named by journalist Joe Tieran as the 'quartermaster' for the bombings appointed by Billy Hanna.
The report does not appear convinced of this, however.
The Baron report said: "It is likely that the farm of James Mitchell at Glenanne played a significant part in the preparation for the attacks. It is also likely that members of the UDR and RUC either participated in or were aware of these preparations."
Mitchell, believed to be now in his early 80s, was an RUC reserve constable. Weir claimed to have seen him making home-made explosives on the farm.
The report also claims that he was first asked by Billy Hanna to store weapons and explosives at the farm.
The report said a description of one of the bombers was said to match the description of UVF member David Mulholland. Although it was also said the man spoke with an English accent.