Royal Nuptials Test U.K. Security Force

LONDON—U.K. security forces are preparing for one of their toughest operations yet: a wedding.

Prince William and Kate Middleton's April 29 nuptials will be attended by government officials, foreign heads of state and celebrities as well as the royal family. The wedding will be a high-profile test case for security forces ahead of next year's Olympic Games here. And it comes amid a heightened terror alert in the U.K. and a string of protests in recent months that have turned violent.

Photos: Security Tight in London

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Metropolitan Police officers carried out security checks on drains and lamp posts along London's Mall ahead of the royal wedding.

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The multimillion-pound security plan for the day is expected to include nearly 5,000 police officers, according to London's Metropolitan Police, known as Scotland Yard. Police will cordon off a chunk of central London stretching from Buckingham Palace to Trafalgar Square, and the area will be closed to traffic.

Plans include an aerial sweep by police helicopters before the wedding, to scan hard-to-see areas like rooftops and railway lines. The helicopters will retreat slightly during the ceremony, so the noise of the blades won't disturb the event, but will continue to monitor the area and the crowd dynamics, beaming images back to a special operations room.

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"There is a lot of pressure on the Met," said Dai Davies, former head of Scotland Yard's royal protection unit. "They know the eyes of the world are watching and will be judging not only the police but the coalition [government], who ultimately will take the blame if something goes wrong."

Security in London is stepped up ahead of next week's royal wedding, as Muslim radicals threaten to disrupt the national celebration. Video courtesy of Reuters and photo courtesy of Getty Images.

A Buckingham Palace spokeswoman directed questions about security to the Metropolitan Police. A police spokeswoman said police have developed plans and tactics from experience of large-scale events over the years, but declined to discuss details. "The royal wedding will be a fantastic day of ceremony and pageantry," she said. "We will take whatever steps are necessary before and during the wedding against those who may want to disrupt this day of national celebration," she said.

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Leading the police effort is Cmdr. Bob Broadhurst, head of public order at Scotland Yard and an experienced hand at such big events. He is heading operational planning for the 2012 Olympics, and was involved in security for Prince Charles's second wedding, to Camilla, duchess of Cornwall.

Cmdr. Broadhurst has said police may use counterterrorism stop-and-search powers during the wedding to prevent the kind of violent disturbances that the U.K. has experienced recently as part of protests against government austerity measures.

The added burden on police comes as the forces face steep budget cuts. The government has said it will cut police budgets by 20% over the next four years.

Police must be alert to a range of threats, from anarchist protesters to Irish republican terrorists to al Qaeda-inspired extremists. The terrorist threat level in the U.K. is currently set by the government at "severe," meaning that generally "an attack is highly likely."

Mr. Davies, the former policeman, said the threats police must plan for today are far greater than at the time of the 1981 wedding of Prince William's parents, Prince Charles and Princess Diana. "The world has changed considerably," said Mr. Davies.

Police will be aiming to avoid incidents such as the December attack by campaigners protesting increases in student fees on the car of Prince Charles, heir to the throne, and his wife, Camilla. Protesters, some chanting "Off with their heads!" smashed a window of the prince's Rolls-Royce and splashed paint on the car as it drove through central London. The couple were unharmed but the incident was an embarrassment for security services.

The car is one of two possible vehicles that Prince William and his bride will use at their wedding; a palace spokesman declined to comment on whether the cars had been fortified since that incident.

That protest was one of several recent demonstrations that turned violent. Last month, more than 200 people were arrested in London on suspicion of criminal damage, violent disorder and other offenses during protests against government cuts. Crowds threw missiles and vandalized a number of buildings, including the Ritz Hotel in Mayfair, a Nike store, and several bank branches. Dozens of people were injured, including police officers. Security for those protests involved thousands of police officers and cost more than £2 million ($3.3 million), according to police.

Among other high-profile security breaches involving the royal family was a famous incident in July 1982 when a man twice broke into Buckingham Palace, once to wander through the kitchens and drink some wine, and later to enter the Queen's bedroom where she awoke to find him at the end of her bed and he engaged her in conversation.

Write to Cassell Bryan-Low at cassell.bryan-low@wsj.com
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