Dramatic phone calls have revealed how the emergency services struggled to cope with the chaos sparked by the July 7 suicide bomb attacks in 2005.
Urgent conversations among key staff were played in public for the first time as the long-awaited inquests into the 52 people killed finally began.
The calls laid bare how London Underground officials were plunged into confusion as explosions rocked Aldgate, Edgware Road and Russell Square stations.
Transport staff were left in the dark as the blasts rendered CCTV systems useless, sent out a blizzard of automatic warning messages and left telephone systems overloaded.
Tube staff were still debating whether the rapidly unfolding tragedy was the result of a power surge or a terrorist attack at least 44 minutes after the first explosion.
Meanwhile, police were reporting bomb blasts and suspected deaths as the walking wounded staggered out of the stricken stations, covered in soot.
One detective at Aldgate declared a major incident, describing the scenes as "pandemonium" as Tube operators elsewhere denied there had been any explosions.
Pc Neal Kemp, another Aldgate officer, called his control room and said: "There is a bomb in a carriage 100 yards into the tunnel. I have multiple casualties, possibly fatalities."
Relatives of those killed more than five years ago wept in court as Hugo Keith QC, for the inquest, outlined how emergency services were delayed by a series of apparent blunders.
He said: "These calls reveal considerable difficulties in assimilating information that is coming in as clearly a very confused incident presented itself."
Coroner Lady Justice Hallett heard that the four bombers - Mohammed Sidique Khan, Shehzad Tanweer, Jermaine Lindsay and Hasib Hussain - committed mass murder with the intention of getting worldwide publicity.
Tanweer, Khan and Lindsay detonated their bombs at Aldgate, Edgware Road and Russell Square at around 8.50am before Hussain blew up a bus at Tavistock Square an hour later.
Their actions were labelled "merciless savagery" that "unleashed an unimaginable tidal wave of shock, misery and horror" for families and friends.