Guests attending the royal wedding will be required to pass through security checks before they can enter Westminster Abbey, though London police have not specified how the screening will be handled.
With only two days to go before Prince William and Kate Middleton's nuptials, police are in the midst of putting the finish touches on an unprecedented security operation to ensure the wedding goes off without a hitch.
Five thousand police officers, some in uniform, others in plain clothes to blend in with the crowd, will be on hand watching for any potential threats to the royal couple, and their families and friends who will be in attendance for Friday's service.
With hundreds of VIPs, including members of the British and foreign royal families, politicians, diplomats and celebrities gathered in one place -- and a worldwide audience watching on television -- a major security breach would be a serious embarrassment.
"We are still engaged in a significant covert and overt police operation," said Lynne Owens, assistant commissioner of the London police, as the agency continued its sweep of locations around the city where a bomb could be hidden ahead of the big day. But while preventing a major incident is the priority, cameras on the ground and in police helicopters flying overhead will be watching the crowd to detect any suspicious behaviour as the wedding gets underway.
Outside the church, it is expected that as many as 1 million spectators will be lining the route between Westminster Abbey and Buckingham Palace on Friday. The royal couple will travel along this route after the wedding service finishes, making their way to the palace for the reception later in the day.
Police are asking spectators to remain on guard for suspicious behaviour.
"We really need you to be our eyes and our ears," Owens told reporters on Tuesday. "If you see anybody in the crowd that is acting suspiciously please bring it to the earliest attention of our officers."
Police are concerned about domestic anarchists that have organized recent demonstrations in London, and dissident republican groups in Northern Ireland that are small but violent.
Dozens of protesters who were arrested during the demonstrations have been banned from the city on Friday. Police also announced last week that they had barred extremist group Muslims Against Crusades (MAC) from protesting outside Westminster Abbey on Friday.
But the most serious potential danger to the royal wedding is the ongoing threat of terrorism, particularly given that London has suffered devastating terror attacks, including the July 7, 2005 bombing of the public transit system.
"The authorities are monitoring a number of challenges," terrorism expert Sajjan Gohel told CTV News. "Nevertheless, we have to face facts that terrorism is a constant threat these days."
Britain's terror alert level is currently at its second-highest warning of "severe," which means an attack is highly likely. However, London police commander Christine Jones told reporters that the force has "no specific intelligence to suggest a threat to this event at this time."
With a report from CTV's London Bureau Chief Tom Kennedy and files from The Associated Press
