By the time Kate Middleton begins her journey to Westminster Abbey on the morning of April 29, snipers from London's Metropolitan Police will have taken their positions on rooftops throughout the city. If a bomb explodes along the parade route, police will siphon crowds into areas that have been blocked to traffic, and ambulances will follow predetermined routes to get victims to various hospitals. Should terrorists launch a Mumbai-style gun attack on the streets, armed commandos, waiting in undisclosed locations, will storm the area within minutes to take out the assailants. "We're at the second highest level of threat that we've ever been in this country, which means an attack is imminent," says Dai Davies, former head of Scotland Yard's Royal Protection Squad and former chief superintendent of the Met (he's not involved in security for the royal wedding). "These threats are very real."
For months, London police, Scotland Yard and MI5 Britain's counterintelligence unit have been considering a slew of ugly scenarios as they prepare for the most expensive security event ever staged in the U.K. The $33 million operation was launched days after the Nov. 16 engagement announcement. Police began digitally mapping key locations from the air to identify weak spots, like rooftops, and intelligence units started tuning into phone conversations and monitored the Internet for chatter of potential wedding terror. At an April 19 security briefing, the Met's assistant commissioner Lynne Owens revealed that a team of 35 specially trained dogs that can sniff bomb materials from 330 ft. (100 m) had already scoured the wedding route. And police have opened up traffic lights, lampposts and water drains along the route, searching for explosives and will recheck them in the coming days. Owens also confirmed that 5,000 police officers will be on duty on April 29, and that authorities have banned 60 convicted criminals from the area surrounding Westminster Abbey as part of their bail terms.
Davies says officials will have isolated a series of groups that pose the most tangible threats. "Fixated individuals" mentally ill people with a pathological focus on someone, often a stranger make up the first group. Forty percent of the most persistent stalkers in the U.K. are fixated on members of the royal family, who together receive around 10,000 correspondences from them each year. Some believe they are marrying William. Others want to harm Kate. As one woman wrote on Prince William's Facebook wall with regards to the wedding: "I will put a stop to this right now." The Fixated Threat Assessment Centre a team of psychologists funded by the Home Office and Britain's National Health Service identify those who pose the biggest threats. "Generally they are reasonably well known. They pop up, they write, they come to these events," says Davies. "But there are ones you don't know about who wake up and suddenly say, 'This is my moment. This is my destiny.'"
A second threat comes from Islamic radicals, including the Yemeni branch of al-Qaeda and the British radical group Muslims Against Crusades. The latter group's website calls members of the royal family "enemies to Allah and his messenger" in part because of Prince Harry's military service in Afghanistan and warns that "the day which the nation has been dreaming of for so long will become a nightmare." On April 19, Scotland Yard denied the group's application to protest outside of Westminster Abbey on the wedding day. Should they make even a nonviolent appearance, a fight between protesters and well-wishers could ensue, causing untold chaos.
The biggest threat, however, may come from dissident Irish Republicans like the Real IRA, who have launched 40 attacks in Northern Ireland within the past year. Authorities have not identified an organized plot, but MI5 recently raised the threat level of Irish-related terrorism from moderate to substantial and shifted its resources from al-Qaeda to IRA splinter groups. In the worldview of IRA militants, an attack on the royal family would be seen as an attack on the British establishment that occupies Northern Ireland. "An attack on the mainland has always been recognized as worth more to them than an attack in Belfast for the publicity it generates," says Martyn Frampton, author of Legion of the Rearguard: Dissident Irish Republicanism and a lecturer at Queen Mary, University of London. "One bomb in London is worth 20 attacks in Northern Ireland."
There's history to the royals being targeted by Irish Republicans. In 1979, the IRA assassinated Lord Mountbatten, the Queen's cousin and a close friend of Prince Charles, by detonating a 50 lb. (23 kg) bomb attached to his fishing boat. And in 1983, authorities foiled an IRA plot to blow up a bomb inside London's Dominion Theatre while Prince Charles and Diana attended a Duran Duran concert.
But it's unclear if any Irish terror group has the capacity to deliver an attack on the British mainland today. None have managed that since 2001, when the Real IRA detonated a car bomb in central Birmingham, causing only minor injuries, and Frampton doubts they can exact tragedy in the face of the wedding's mammoth security detail. "But even a hoax bomb can cause disruption on the day," he says. "As much as the act of actually killing someone, there is probably value for them in causing disruption and showing that they have the capacity to disrupt a major event."
To mitigate the risks of attacks from any of the groups, many of the 5,000 police officers on duty will be dressed in plain clothes and embedded among the expected 500,000 well-wishers. Arriving in the early hours of the morning, they will "get to know their crowds" and identify potential threats, information that they can feed to other officers along the route. To boost the surveillance offered by the city's thousands of CCTV cameras, three patrol helicopters with high-definition video cameras will circle above the city. And, given Westminster Abbey's proximity to the Thames, contingencies will have been made for Mumbai-style attacks launched from the river. As for the VIP list, which includes 50 heads of state, the Met's Owens said they'll have the added security of up to 80 "close-protection units" security speak for highly trained teams of bodyguards to escort them around the city.
If all goes according to plan, the newly minted Catherine Windsor will kiss her husband on the balcony of Buckingham Palace around 2 p.m., before retreating to a more private reception with friends and family. And while the public pomp will end there, the work of security officials will continue. "Everybody thinks, 'What will happen on the day?' But I would be looking at the days before, and the days and weeks after," Davies says. "There's a tendency for everyone to relax when the main event is over and then, bang! Britain can't take its eye off the ball for some time."
With reporting by Tara Kelly / London