Britain will open long-awaited inquests on Monday into the deaths of 52 people in the 2005 London bombings to probe alleged failings by police and intelligence services before the attacks.
A judge ruled in May that the inquests could go ahead after a campaign by the survivors and relatives of those killed in the suicide explosions that ripped through three London Underground trains and a bus on July 7, 2005.
The British government has ruled out holding a full independent inquiry but the inquests will be able to look into whether police and the domestic intelligence service MI5 could have done more to prevent the attacks.
The bereaved relatives have said they want to ask why security officials did not act to stop bombers Mohammad Sidique Khan and Shehzad Tanweer despite having monitored them in early 2004.
"I want the inquests to look at whether any mistakes were made or flawed systems were in place," said Ros Morley, whose husband Colin, 52, died in one of the Underground bombings.
"Innocent citizens in the UK and worldwide need to know that they are protected now and in the future.
"I hope it is possible to gain something positive out of a deeply tragic event in which 52 innocent people lost their lives."
New details have already emerged in documents submitted ahead of the inquests, including that police discovered they had held the fingerprints of Khan, the ringleader, on file from as far back as 1986, when he was 11.
The documents also revealed that 17 of the people killed in the blasts did not die instantly, with at least one victim having survived for up to 40 minutes after one of the attacks.
MI5 has sought to block much of the questioning on the grounds that it would require the disclosure of secret files that would threaten national security.
In May, coroner Heather Hallett said the "scope of the inquest into the 52 deaths will 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. Plots of this kind are not developed overnight," she added.
The legal battle over whether the confidential information should be aired at the inquests is not expected to begin in full until next year, with the early part of the hearings set to be largely procedural.
Inquests into the deaths of the four, homegrown bombers will be held separately at the families' request.