Fifty-two people were killed by the 7 July suicide bombers
Inquests into the deaths of 52 people killed in the 7/7 bombings will examine the alleged failings of MI5 in the run-up to the attacks, a coroner has ruled.
Lady Justice Hallett told the Royal Courts of Justice it was still possible to investigate what security services knew before the 2005 London attacks.
She also ruled the inquests of the four bombers would not be heard at the same time as those of the victims.
Victims' families said they hoped they would finally find out what happened.
Bereaved relatives have long campaigned for the inquests to investigate whether the attacks could have been prevented after it was revealed two of the bombers had cropped up in a surveillance operation more than a year before.
There is hope that finally the question, could 7 July have been prevented, might be answered
They also want to know if there were any failings in the emergency response that followed.
Clifford Tibber, from the firm of solicitors representing many relatives, told a news conference the coroner's decision had sparked mixed feelings among relatives.
There was disappointment that the legal process had taken so long but also optimism that they would now learn "what actually happened to their loved ones", he said.
"There is a hope that if the response of the emergency services did in any way fail those who needed treatment, that lessons will have been learnt from those failings and that appropriate measures will be put in place in future to ensure it does not happen again.
"There is hope that finally the question, could 7 July have been prevented, might be answered," he added.
However, Mr Tibber did not rule out calling for a further public inquiry.
Prime Minister David Cameron asked questions about whether an inquiry would be held while in opposition and his deputy Nick Clegg had previously called for a full public inquiry, he added.
'Faith in coroner'
Fifty-two people died when suicide bombers struck aboard Tube trains near Edgware Road, King's Cross and Aldgate and on the number 30 bus at Tavistock Square, all in central London.
Janine Mitchell, whose husband Paul survived the King's Cross explosion, said she hoped the inquests would be a chance to finally learn about the role of the security services ahead of the attacks.
"We do not know what went on and we are relieved that someone independent of government is going to examine what happened," she told the news conference.
Again we have be shunted aside by officialdom
Survivor Jacqui Putnam
"We put all our faith in the coroner to do that, so if anything did go wrong it can be fixed."
Ros Morley, whose husband Colin was killed in the bombings, welcomed the ruling not to hold the bombers' inquests at the same time as those of their victims.
"It is absolutely the right decision," she said.
However, there was disappointment among the survivors after Lady Hallett confirmed that although she would give victims' relatives and the emergency services "interested persons" status, survivors would not receive the same right to question witnesses.
Jacqui Putnam, a survivor of the Edgware Road bombing, said she feared the coroner's decision would deny her and fellow survivors a proper voice.
"Our role now will be one of answering questions only - which we will do willingly, but our questions are not going to be answered unless they are asked by someone else who is one of the bereaved," she said.
"Again we have be shunted aside by officialdom."
Lady Hallett earlier explained in court that the inquests into the 52 deaths, which will be heard without a jury, would include the "alleged intelligence failings and the immediate aftermath of the bombings".
"To my mind it is not too remote to investigate what was known in the year or two before the alleged bombings," she said. "Plots of this kind are not developed overnight."
7/7 inquests 'chance to tell story'
Many of the bereaved families want to find out why the security service did not follow up the bombers' ringleader Mohammad Sidique Khan after he was witnessed meeting a known terror suspect 17 months before the attacks.
However, lawyers for MI5 have argued this evidence would give al-Qaeda an "invaluable weapon" and should not be disclosed.
Lady Hallett said that sitting without a jury would mean such sensitive intelligence material could be "more effectively examined", but she added that the secret nature of the evidence might limit the extent to which the issue could be explored.
Khan, 30, from Dewsbury, near Leeds, carried out the attacks with three other suicide bombers.
The 7/7 inquests are expected to begin in October at London's Royal Courts of Justice. They have been delayed by court cases connected to the bombings.
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