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.
The inquest heard that the emergency response was marred by a series of failings that might have delayed urgent medical care to those underground. They included:
:: Staff at the London Underground co-ordination centre continued to tell colleagues the incident was not terrorist-related at 9.32am, 44 minutes after the first explosion;
:: The Piccadilly Line manager, based at Earls Court, could not make outgoing calls from 9am onwards because the telephone system was overloaded;