Vigilant British authorities have built multiple layers of heavy security around the parade route Prince William and Kate Middleton will take for their April 29 royal wedding. The so-called "ring of steel" will guard against potential terror threats to the royal couple from Al Qaeda, anarchists and IRA splinter groups, among others.
From making full use of London's robust closed circuit television (CCTV) camera system, to dispatching hundreds of undercover police officers and even inspecting and sealing sewer drains, authorities are pulling out all stops to protect the prince, the future princess and the throngs of spectators expected to turn out for the wedding procession, officials told ABC News. Though there has been no specific threat against the wedding, bomb-sniffing dogs, hazardous material teams, riot police and roof-top snipers will be dispatched on the day of the ceremony, and foreign intelligence services will also be participating in the massive security effort, they said.
From special police command centers hooked up to the CCTV system, authorities can keep an eye on hundreds of people at once, according to British Transport Police Chief Constable Andrew Trotter.
Trotter gave ABC News an inside look at one of the command centers used for special events like the royal wedding. On the center's huge bank of monitors, operators can watch Buckingham Palace, Westminster Abbey, or zoom in on crowds to check out suspicious packages and individuals, Trotter told ABC News. A toggle switch allows extremely tight close-ups of faces in hundreds of public places all along and around the wedding route.
"I wouldn't want to operate on any major event without it," Trotter told ABC News. "I love the pictures. ... It's a great tool and there will be more and more of it."
Security officials are prepared to sift through the flood of images using "Cognitive Visual Affirmation," a sophisticated technique in which experts watch for body movements that might indicate a person could be a threat. In addition, Trotter said officers will keep using another, more traditional technique: looking for anything strange.
"It will be something that is a bit unusual, for example, people hanging around for a long time, letting trains go by before they get on. Just strange behaviors, people looking out of place," he said.
England's terror threat level has been at "severe" since January 2010. Security experts in London told ABC News the wedding has a higher threat profile than any previous royal event and regular meetings of COBRA, the British national emergency committee, have been increased recently.
And, in this case, authorities are preparing for threats from not one group, but three.
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The high-tech police commander centers were not in place six years ago when Islamist terrorists attacked the London underground and bus system, killing more than 50 people.
Since then, authorities have arrested dozens of Al Qaeda-inspired, Al Qaeda-directed and "self-radicalized" terror suspects across the United Kingdom and disrupted what they said were many more Islamist plots.