London: Four suicide bombers who killed 52 innocent people in the July 7, 2005 London attacks may have been planning to strike the day before, inquests into the deaths heard Monday.
The opening day of the long-awaited inquests also heard recordings of a flurry of phone calls to the emergency services, gradually revealing the chaos wreaked by the bombing of three Underground trains and a bus.
The hearing heard that the attacks may have been timed for July 6, the day London partied as it won the right to host the 2012 Olympics.
The plot ringleader, Mohammed Sidique Khan, sent a text message at 4:35am on July 6, apparently abandoning a meeting due to a "major problem".
Hugo Keith, counsel for the inquests, said mobile phone traffic revealed that Khan texted another of the suicide bombers, Shehzad Tanweer, the previous day.
The message read: "Having major problem. Cannot make time. Will ring you when I get it sorted. Wait at home."
The inquest heard that Khan visited a hospital with his wife on July 5 due to complications with her pregnancy and she miscarried on the day of the attacks.
Keith told the inquest: "It may have been that the attack was originally planned for a different day."
The chaos of July 7 was recalled when the inquest was played a series of telephone calls between the Underground network control centre, the stations affected and the emergency services.
The conversations showed that the explosions were not initially believed to be terror attacks, but the seriousness of the situation progressively became clearer.
What started as reports of an explosion at one station, Aldgate, and what was thought to be a power problem swiftly escalated with casualties emerging from the tunnels and emergency services rushing to the stations.
Aldgate station supervisor Celia Harrison said in one early call: "We`ve just had a big explosion... they said something has exploded at the head of the train.
"We`ve had thick smoke coming from the tunnel, we`ve had customers on the track.
"Will you please get as many ambulances as you can here, we`ve got injuries.
"I`ve seen people coming up covered in smoke and injured."
In his opening statement, Keith, whose role is to present information to the coroner in the hearings, said the bombs "detonated amongst the innocent and the unknowing, indiscriminately killing and maiming passengers who were simply going about their daily business."
The suicide bombers had unleashed an "unimaginably dreadful wave of terror and horror", he said.
He warned relatives of the dead that some of their questions may never be answered.
But he added: "We are confident that these inquests can deliver meaningful conclusions about the indirect as well as direct causes of the deaths."
The inquests, presided over by judge Heather Hallett, acting as coroner, had been delayed pending the trials of the alleged conspirators of the four suicide bombers.
The 484 witnesses to the inquests will include survivors of the attacks and members of the emergency services who desperately tried to save lives.
The British government has ruled out holding a full independent inquiry into the attacks but the inquests will be able to look into whether police and the domestic intelligence service MI5 could have done more to prevent them.
Survivors and bereaved relatives have said they want to ask why security officials did not act to stop Khan and Tanweer despite having monitored them previously.
Speaking before the inquests started, Ros Morley, whose husband Colin, 52, died in one of the Underground bombings, said: "I want the inquests to look at whether any mistakes were made or flawed systems were in place.
"Innocent citizens in the UK and worldwide need to know that they are protected now and in the future."
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.
The coroner said as much of the evidence as possible would be disclosed.
"I will balance carefully the needs of national security with relevance and fairness," she said, but pledged to conduct the inquests "in as open a manner as possible".
Inquests into the deaths of the four bombers will be held separately at the families` request.
The four near-simultaneous attacks unleashed a wave of unease about the threat of homegrown extremism, especially when it emerged that some of the bombers had visited Islamists in Pakistan.