That heightens the possibility that the bombers simply stepped off as the doors closed, and may have been back on the street when the bombs exploded within 50 seconds of each other.The principal mystery surrounds the fourth explosion, which killed 13 people on a bus in Tavistock Square. Most of them have very tight-knit cells, with eight to 10 individuals or so, who have personal links that go back for years."Dealing with this threat is a nightmare for counter-terrorist agencies, but many question whether it makes sense to label the struggle as a war. "Even though this is pure revenge terrorism, with no negotiable demands, you still have to try to understand what they want to achieve," said George Kassimeris, a senior research fellow in conflict and terrorism at the University of Wolverhampton. In the last few years, these groups seem to have adopted a very cellular structure. Two arrests in particular, those of Ramzi Binalshibh in September 2002 and Khalid Sheikh Mohammed in March 2003, both in Pakistan, disrupted its ability to direct attacks.The two men have disappeared into American custody, along with other senior figures such as Abu Farah al-Libbi, said to have replaced Sheikh Mohammed, and Abu Zubaydah, described as bin Laden's field commander. Presumed to be hiding in the tribal borderlands straddling Afghanistan and Pakistan, communicating only by written notes and the occasional hand-delivered cassette or video tape, he is in no position to exert day-to-day control over terrorist attacks."The good news is that it is difficult for bin Laden to issue orders and direction to people now," an intelligence official said.
"The bad news is that it is harder to track and stop inspired groups who leave fewer footprints, communicate less and don't need to travel as far."Arresting bin Laden or his deputy, the Egyptian physician Ayman al-Zawahiri, would have huge symbolic significance, depriving al-Qa'ida of its ideological focus But its operational capacity has already suffered. "I imagine they are just taking it all in, which is normal at this stage. I am not really encouraging them to talk about it, if they want to we will listen but they will probably want to talk about it with their friends and families.". Every atrocity such as the London bombings raises the same questions: was al-Qa'ida responsible? If the network was not directly involved, did it give the attack its blessing? Is Osama bin Laden still giving the orders? And where is he hiding? If we are fighting a "war on terror", then al-Qa'ida is clearly the enemy.
But even before it was disrupted by the fall of the Taliban in Afghanistan, and the arrest of many members of its inner circle, it was never an organisation with a clear hierarchical structure. It has always been as much an ideology as a tangible group. "Trying to hit al Qa'ida is like trying to hit jelly," said one intelligence source. "One minute you think you know who is running it, and next minute you feel you have no idea."Bin Laden himself, even before the attacks of 11 September 2001 turned him into a fugitive, was as much a figurehead as a strategist. "The way people reacted and the spirit of people in London was very good. In the hospital it was really very calm, there were no chaotic scenes.
