A British Government decision to refuse a public inquiry into the Omagh bombing is to be challenged in court.
A judge at Belfast High Court today granted leave for the father of the one of the victims of the Real IRA outrage in 1998 to take judicial review proceedings against Northern Ireland Secretary Theresa Villiers.
In 2013 Ms Villiers ruled out an inquiry, claiming she did not believe there were sufficient grounds to justify a state-commissioned independent probe.
Some of the bereaved relatives have long campaigned for such an inquiry into alleged state intelligence and investigative failings.
The families claim mistakes allowed the bombers to perpetrate the atrocity.
The dissident republican attack which killed 29 people, including a woman pregnant with twins, and injured hundreds more was one of the worst atrocities of the Northern Ireland troubles and inflicted the greatest loss of life in a single terrorist incident.
No one has been convicted of the bombing but Seamus Daly, a 44-year-old bricklayer from Cullaville, Co Monaghan, is on remand in jail charged with the murders - counts he denies.
Michael Gallagher, whose 21-year-old son Aiden died in the bombing, is taking the judicial review proceedings.
He represents one of a number of families pressing for the inquiry, many of whom belong to the Omagh Support and Self Help Group.
After the hearing Mr Gallagher described the development as the "first foot on the ladder".
"This is but a step on our continued fight for justice," he said.
"Today the courts have agreed at the very least that the Secretary of State's decision was questionable.
"We will now move on to prepare for a full hearing before the courts to show that the state has yet to properly investigate the circumstances of the Omagh bomb."
With the bomb having been allegedly transported to the Co Tyrone town from the Republic of Ireland, bereaved families have called for a cross-border inquiry involving the London and Dublin governments.
Not all the Omagh families support the campaign for an inquiry, with some claiming the exercise would only re-traumatise victims.
The judicial review is expected to be heard in April.
The decision was welcomed by Amnesty International.
Amnesty's Northern Ireland director Patrick Corrigan said: "The Secretary of State's decision not to hold an inquiry into the Omagh bombings was a betrayal of the victims and families who have longed for answers for over 16 years.
"All that families want is the truth, yet the Government slammed the door in their face."