After more than five years of delay that have angered and frustrated the victims' families, an inquest opened on [October 11] into the [attacks] on the London transit system on July 7, 2005, that killed 52 people and the four bombers, and wounded more than 700 others. The inquest ... began with the presiding judge, Lady Heather Hallett, ... pledging in her opening remarks that she would undertake to keep the inquest as open as possible while protecting Britain's national security. Lady Hallett said she would go as far as she could to meet the demand of the victims' families to know why the country's security and intelligence services did not act to prevent the bombings on the basis of what they knew about the attackers beforehand. The families' demands have echoed those of victims' relatives after the Sept. 11, 2001, attacks in the United States, but they have been amplified by the lengthy delay in holding the London inquest, which is the first comprehensive public inquiry into what have become known in Britain as the 7/7 attacks. The delay in opening the inquest has been officially explained as necessary to allow the police and other security agencies to complete their own investigations. As with the last inquest in Britain to become a focus of attention on a similar scale, the long-delayed investigation into the 1997 death in a Paris car crash of Diana, Princess of Wales, top officials of Britain's major police and security agencies, Scotland Yard, MI5 and MI6, are expected to be called as witnesses.