The Omagh bomb atrocity will be investigated to a standard that meets human rights requirements, a High Court judge said on Friday.
Lord Justice Horner made the pledge after the UK government announced an independent inquiry into the August 1998 Real IRA attack that claimed 29 lives.
On Thursday Northern Ireland secretary Chris Heaton-Harris confirmed his intention to establish the statutory inquiry to examine issues previously identified by the judge.
Lord Justice Horner ruled in 2021 that the bombing could arguably have been thwarted if police had received all available intelligence.
‘It’s been retraumatising’: Families of six men shot dead by British soldiers seek truth 50 years on
He recommended fresh probes on both sides of the Irish Border, based on a legal duty under Article 2 of the European Convention on Human Rights (ECHR).
The verdict came in a judicial review challenge by Michael Gallagher, whose son Aiden was among those killed in the outrage.
Mr Gallagher is continuing his legal battle amid alleged government delays and failures to act on the judgment.
In court on Friday Lord Justice Horner indicated there has been “a positive response” in attempts to ensure the Omagh bombing is the subject of a probe that meets ECHR standards. He also stressed a determination to have its findings implemented.
The judge said: “To leave nobody in any doubt, I am absolutely intent that the judgment will be put into force and there will be an Article 2 compliant investigation.”
No one has ever been held criminally responsible for the bombing which inflicted the greatest single loss of life during the Troubles in Northern Ireland.
The 29 people who died included a woman pregnant with twins. Hundreds more were injured in the attack.
Initial proceedings focused on claims that intelligence from British security agents, MI5 and RUC officers could have been drawn together to foil the car bomb plot.
Lord Justice Horner held that full sharing of surveillance and mobile phone tracking evidence may have disrupted dissident republicans behind other attacks in the months leading up to the attack on Omagh.
Identifying a potential failure in policy at the time around a de-escalation of security, he said it was also arguable that a tip-off from an undercover British agent could have contributed to the chances of averting the explosion.
No conclusive determination was reached that the atrocity could have been avoided.
But in the 2021 ruling, he pointed to “plausible arguments that there was a real prospect of preventing the Omagh bombing”.
Mr Heaton-Harris announced the inquiry is to be established as promptly as possible to examine a number of areas identified in that judgment.
Counsel for Mr Gallagher told the court today: “It’s a very welcome and significant development.”
Adjourning the case to next month, Lord Justice Horner urged both sides to continue discussions aimed at resolving any outstanding issues.
He added: “I am content at the moment with what I have seen, but we want to get the whole matter resolved.”