Inquests into deaths of 21 people in the 1974 Birmingham pub bombings are to be reopened, a coroner has ruled.
Louise Hunt said there had been a "wealth of evidence that still has not been heard" about the atrocities.
The double bombing on 21 November 1974 is widely acknowledged to have been the work of the IRA.
It was the worst terrorist attack in Britain until the 7/7 bombings in London and left 21 dead and 222 injured.
The original hearings, opened days after the attacks, were not continued after the jailing of six men, whose convictions were later quashed.
Julie Hambleton, whose 18-year-old sister Maxine was killed in the blasts, said: "All we want is to be heard - truth, justice and accountability."
Ms Hunt, the senior coroner for Birmingham and Solihull, heard there was evidence police had missed two potential warnings of the bomb attacks.
It included a comment made by men linked to the IRA in an overheard conversation that "Birmingham would be hit next week".
But, West Midlands Police had argued the coroner did not have the jurisdiction to hear the inquests, however Ms Hunt rejected their submission.
As recently as 12 May, the force's barrister Jeremy Johnson QC argued there was "simply no evidential basis" for reopening the hearings.
He added that it was the force's view that the "pieces of intelligence" it received from time to time about possible attacks could not "on a fair analysis" amount to advance warning of the bombings.
The blasts destroyed the Mulberry Bush pub at the base of the city's landmark Bullring Rotunda and the underground Tavern in the Town.
Those responsible have never faced justice and the only men to be tried for the crime - the Birmingham Six - had their convictions overturned by the Court of Appeal in 1991 after 16 years in prison, after a botched investigation by the West Midlands force.
Ms Hunt reviewed a huge body of police evidence and heard submissions from the victims' relatives and other interested parties in February.
The hearing was told that the overheard conversation was reported to police on 10 November 1974, 11 days before the bombings, but Ms Hunt said there was "no indication that the police took any active steps in response to it".
On the day of the attack, a second tip-off to the police was not followed up, she added.
Ms Hunt went on: "I have serious concerns that advanced notice of the bombs may have been available to the police and that they failed to take the necessary steps to protect life."
Mrs Hambleton, who has led the campaign for justice with her brother Brian, said she hoped the truth would finally come out.
Outside the coroner's court in Solihull, she said: "Today, we stand united. I'm so proud of all the families, legal team and you (the media).
"I cannot put into words how we feel... we've been crying.
"An inquest gives us the opportunity to hear from people you wouldn't normally hear from and it can lead to all sorts of things... the truth... the truth is fundamental."
One of the six wrongly convicted men, Paddy Hill, said outside the court: "They (police) don't want [the inquests] because there's too many skeletons in the cupboard.
"They had advanced warning and they took no notice. I don't think Birmingham police could spell truth - they're rotten.
"I'm very sceptical about getting the truth."
Following the release of the Birmingham Six, a reinvestigation was opened, led by the then Chief Constable for the West Midlands, Ron Hadfield, and the Director of Public Prosecutions (DPP), Barbara Mills.
A team of 40 officers generated 5,000 documents, statements and reports. In 1994, they concluded there was insufficient evidence for proceedings against any person, and the inquiries had been carried out were to the satisfaction of the DPP.
Ms Mills placed a 75-year embargo on files relating to a Devon and Cornwall Police inquiry into the West Midlands Police investigation.
Analysis - News correspondent Phil Mackie, outside the hearing in Solihull:
The coroner went through the names of the 21 people who lost their lives and the events of the night and the evidence she heard over the past few months.
She said she had no doubt that ascertaining the truth about what happened on the night of 21 November would be difficult but that there was evidence that needed to be heard.
But she said with a note of caution, families and survivors may not get the answers that they want as the inquest could be inconclusive.
What happens next is pre-inquest hearings where we'll hear from West Midlands Police, the Police Federation, fire and ambulance and the government - they will have to go through its archive - and we'll hear from MI5 and the Foreign Office.
But it won't be until next year when we have a full hearing.
The campaign to resume inquests has escalated in recent years as the victims' families fought for justice.
Maxine Hambleton's brother Brian said he was "overwhelmed" at hearing the result and that his emotions "just took over".
"I just thought about my sister, the atrocity... and West Midlands Police are battling so hard to prevent the truth from coming out. But luckily, coroner Louise Hunt is allowing the truth to come out now.
"The truth will prevail. I believe that and that's what keeps me going."
Despite the force's opposition to the families' legal bid, West Midlands Police Chief Constable Dave Thompson said he welcomed the coroner's decision.
"West Midlands Police not only failed to catch those responsible but caused a miscarriage of justice," he said.
"I have said, and reiterate again, it is the most serious failing in this force's history.
"I understand families of those who lost their lives are frustrated, disappointed and angry.
"West Midlands Police will support this inquiry as we have done through the recent hearings by the coroner which determined whether the inquest should reopen. I hope the new inquest provides answers to families."