The inquests into the deaths of the 52 victims of the 7/7 suicide bombings cost more than £4.6 million, official figures show.
This included over £2.2 million for external legal services, £685,581 for IT services, £600,000 for accommodation and £265,262 for staff.
In total the five-month hearing at the Royal Courts of Justice into the July 7 2005 attacks on London's transport network came to £4,604,721.
Coroner Lady Justice Hallett heard evidence between October 2010 and March 2011 before ruling last May that the emergency services could not have saved any of those who died in the bombings on three Tube trains and a double-decker bus.
But she also raised serious concerns about how MI5 investigates and prioritises suspects, warning that poor record-keeping could allow flawed decisions to slip through with "dire consequences".