Fresh inquests have been ordered into a loyalist bomb attack that killed 15 people in McGurk's Bar in Belfast city centre in 1971.
Two children were among those who died.
Security forces in Northern Ireland initially blamed the IRA, prompting speculation that the dead included IRA members who had been carrying the device.
But this was disproven and responsibility for the murders was attributed to the UVF.
The families of the victims believe the security forces had knowledge of the attack in advance and could potentially have prevented it.
It has also been claimed that the decision to initially blame the IRA was part of a British military intelligence propaganda strategy aimed at undermining support for the organisation.
Attorney General for Northern Ireland Brenda King informed a family in the case yesterday that she has ordered new inquests into the deaths.
Gerard Keenan was 13 when his parents Edward and Sarah were killed.
He welcomed the decision, saying the families of all those killed had been "fighting far too long" to overturn the original inquest findings, which recorded an open verdict and did not attribute blame for the attack.
"Our families welcome the historic decision of the Attorney General to direct a new inquest as all the families have campaigned with great dignity for over 52 years for scraps of truth and justice from the British state," he said.
"Like many other bereaved families now, though, we face the reality that the British state will not allow this inquest to go ahead as it desperately wants to stop us from discovering why our loved ones were murdered in the McGurk's Bar massacre and how it failed to prevent it."
At this stage the Attorney General's direction for new inquests is technically limited to the deaths of Edward and Sarah Keenan, but solicitors representing other families said they believe it is now just a formality that there will be fresh inquests into all 15 killings.
"You can't differentiate between those who were killed," says Christoper Stanley of KRW Law in Belfast.
"They were all killed by the same bomb so any investigation must examine all of the deaths.
"Today we have written to the Attorney General to include those victims whose relatives are instructed by KRW or to confirm that her direction includes those victims."
The new inquests were ordered after new evidence about the attack was uncovered by a grandson of one of the victims.
Ciaran MacAirt, whose grandmother Kathleen Irvine was killed in the attack and his grandfather John badly injured, has spent years investigating the circumstances of the bombing.
He provided the Attorney General with evidence that British military observation posts were operating in the vicinity of the bar.
In a letter to Gerard Keenan, the Attorney General said "investigations of the actions or inactions of the army in the period before the bombing occurred is incomplete".
A solicitor representing Mr Keenan described the decision as "hugely significant" and said he hopes the decision will result in the family finally getting the truth about what happened.
"There was a huge cover up in this case, tens of millions of pounds was thrown at it by the British state which has been ongoing, but this is the opportunity where the record will be set straight," said Niall Ó Murchú.
There has been a clearing of the decks when it comes to legacy in recent weeks with coroners and the Attorney General issuing a number of directions about fresh inquests and public inquiries.
However, as it stands those decisions mean nothing and the families involved will not get the answers they have been seeking because a legal guillotine halting all legal proceedings relating to killings during the Troubles comes into effect next Wednesday.
Legacy inquests which have not reached the point of verdict by 1 May will be transferred to the Independent Commission for Reconciliation and Information Recovery (ICRIR).
A High Court judge in Belfast ruled earlier this year that the legislation is unlawful as it is not compatible with the human rights legislation.
But the British government is pressing ahead. A number of legal firms have said they will seek to repeal the Legacy Bill.
