By Jamie Doward, Mark Townsend, Anthony Barnett, David Smith, David Rose and Paul Harris
At dusk last Thursday a man could be seen shuttling between a white van and a nondescript flat sandwiched in a row of houses on Forest Road in Walthamstow, east London. The van parked outside the flat was no ordinary van. Inside were racks of equipment -- cameras, brushes, flashlights -- all the forensic paraphernalia used in modern police investigations.
The flat was guarded by two police officers dispatched from Walthamstow police station a short walk away. Across Britain -- in east London, High Wycombe and Birmingham -- similar scenes were being played out as police searched the homes of the 24 terrorist suspects who had been arrested earlier in the day under suspicion of plotting a massacre which, according to officials, would have been on an "unimaginable scale."
The Forest Road flat is unlikely to throw up too many new leads, however. According to neighbors, the two men who used to live there, believed to have been of North African origin, left more than a month ago.
"It was sold overnight," a neighbor said.
"One day it was up for sale and the next it was gone. I think two men moved in the following weekend. No furniture was moved or anything -- it was really strange," the neighbor said.
The two men's whereabouts remains unknown. It is not clear whether they are still at large, part of a disparate group of terrorist suspects who the police are still looking for.
According to an internal US Department of Homeland Security document, as many as 50 people were involved in the alleged plot to blow up 10 transatlantic airliners, a figure that British intelligence sources -- who insist all the main suspects have been rounded up -- have declined to comment on. But if correct it suggests the "second phase," as intelligence officials term the period that follows the initial arrests, is going to be as equally complex as the 12-month operation that led to last week's raids.
As British Home Secretary John Reid acknowledged on Saturday: "We're not yet at the stage where we can or should stop searching. That is why the alert level remains at critical as a precaution."
The security services' preference would have been to wait as long as possible, allowing the police to continue their surveillance in the hope of arresting all those suspected of being involved. The botched raid on a Forest Gate home in May had made all involved in anti-terrorism wary of acting too soon. But this was a luxury they could not afford.
The intelligence services had been tipped off that an attack was to take place within the next couple of weeks. It is believed that money had already been wired through for the suspects to buy their plane tickets, suggesting an attack -- or possibly two waves of attacks, several days or weeks apart to maximize their terrifying impact -- was imminent.
Over the next few days, following that money trail will be crucial to the intelligence agencies as they attempt to build a case against the suspects and gain a clearer picture of whether many young people, all British-born, would want to martyr themselves and kill thousands -- and if so, why.
Follow the money
Follow the money trail, intelligence experts say, and you can track the suspects. The money came from Pakistan.