Huge volume ofevidence on file
The Metropolitan Police investigation database is the largest ever created.
Coroner Lady Justice Hallett must sift through a deluge of information from police, MI5, other emergency services and eyewitnesses, as well as CCTV, forensic and technical details.
She said as much evidence as possible would be considered in public and no decision had been made on whether she would sit in secret for sensitive intelligence material.
There have already been a series of investigations into the 7/7 attacks, including major reports by the Parliamentary Intelligence and Security Committee and the London Assembly.