The confusion and delays that followed the 7 July bombings in London have been highlighted by a series of emergency calls played at the victims' inquests.
London Underground operators at first attributed explosions and "thick black smoke" to a power failure.
"Considerable" time elapsed before they accepted they were dealing with bombings, the inquest heard. The father of one victim called it "shambolic".
The bombers - who murdered 52 people - were "merciless", the inquests heard.
Coroner Lady Justice Hallett requested a minute's silence before the hearings into the attacks on three Tube trains and a bus began.
She will examine how each victim died and whether MI5 could have stopped the bombers. Many families still want a public inquiry.
In addition to those killed, some 700 people were injured, many of them severely and permanently, when four al-Qaeda-backed suicide bombers, all British men, detonated their devices.
Mr Keith said bombers Mohammad Sidique Khan, Shehzad Tanweer, Germaine Lindsay and Hasib Hussain had unleashed an "unimaginably dreadful wave of horror".
"They were acts of merciless savagery which could only outline the sheer inhumanity of the perpetrators."
He added: "The essential nature of these acts was murder."
After the inquest opened on Monday, a series of emergency calls between supervisors at Tube stations, London Underground control centre and emergency services revealed the deep sense of confusion in the aftermath of the blasts.
The first calls played to the court reported suspected power failures, but the emerging picture became more serious as the operator received further reports of a "bang", walking wounded and passengers in the tunnels.
Shortly after the attack at Aldgate, one caller tells the operator: "We have just had a big explosion, there appears to be something ahead of the train on the track. We have evacuated."
The caller is asked for more precise details but is unable to give more information.
In the next recording, the operator is heard calling emergency services but shows a reluctance to deploy rescue workers, saying: "We don't want to send anyone at the moment."
Describing the reports, he adds: "We are not looking at an act of aggression."
In another call, the operator is told one Tube station was "lit up like a Christmas tree".
Following the three Tube bombings at 0850, Steve Gozka, manager of Edgware Road Tube station, rang London Underground's Network Control Centre (NCC) at 0906 to repeat a request for the emergency services to be sent.
"Something's gone badly wrong down there," he says.
Mr Gozka was one of the first London Underground managers to suspect the incidents were terrorism-related.
The operator is heard telling callers the incidents are not believed to be terrorist-related, but later tells an official from the Railway Inspectorate that the explosions were either caused by terrorism or by a power cable.
"I'm leaning towards terrorism at the moment, but I can't tell you that," he says.
Mr Keith told the coroner: "Those calls reveal considerable difficulties in assimilating the information that is coming in, and plainly a very confused picture presented itself."
He added that despite the bombs having exploded out of public sight, it was "rather surprising" that no one at the scenes, having seen the damaged trains or spoken to passengers or drivers, was able to phone the NCC and say "definitively that there have been bombs".
"A considerable amount of time had elapsed... from the moment of the explosion of the bombs to the acceptance by the staff of the NCC that they were bomb-related," he said.
Graham Foulkes, father of 22-year-old David - who was killed at Edgware Road - said it was "clearly shambolic".
"They were clearly unprepared and they had clearly not been trained to deal with any... major event whatsoever," he told the BBC.
Earlier the inquest heard that the attacks may have been planned for the previous day, but appear to have been called off by ringleader Mohammad Sidique Khan.
He texted fellow bomber Shehzad Tanweer at 0435 on 6 July saying: "Having major problem. Cannot make time. Will ring you when I get it sorted. Wait at home."
The inquest heard that Khan visited Dewsbury Hospital with his wife on 5 July because of complications with her pregnancy. She miscarried on the day of the attacks.
The hearings at the Royal Courts of Justice in London are expected to last until at least March next year and will look into the precise details of the 2005 attacks.
Witnesses will include survivors of the attacks on underground trains near Aldgate, Edgware Road and Russell Square Tube stations, and on a double-decker bus in Tavistock Square, near King's Cross.
Members of the emergency services will also give their accounts, and many of the victims' relatives are represented in the inquests and will be able to question witnesses.
Lady Justice Hallett will preside over the hearings without a jury.
There have been two official reports into the bombings by the Intelligence and Security Committee in Parliament, both of which said that MI5 should not be blamed.
The hearings had been delayed because of criminal investigations and questions over what the inquests should cover.
The inquests of the suicide bombers have been adjourned and will be held separately.