It was a wrong-place, wrong-time brush with danger: Protesting students -- some chanting "Off with their heads!" -- attacked Prince Charles and his wife Camilla as they rode in their vintage Rolls-Royce to a charity event at a London theater.
How could the mob have gotten so close, so easily, to the future king?
There was no quick answer Friday, amid scathing criticism from security experts and calls for officials to be fired.
The royal couple were unharmed but visibly shaken Thursday after the angry protesters, pumped up by earlier scuffles with police, surrounded their luxurious dark limo, smashing a rear window and splashing it with white paint.
Video and pictures from The Associated Press captured it all: Camilla, her mouth wide in horror, grasping for Charles as the rowdy crowd pummeled the car. Both were in full evening dress, Camilla's glittering emerald and diamond necklace nestled against the green satin ruffle of her coat.
Buckingham Palace does not comment on royal security procedures, but security experts identified a host of failures surrounding the royal outing -- and warned that procedures must be dramatically improved before Prince William's wedding to Kate Middleton at Westminster Abbey this spring.
"It wasn't potentially dangerous -- it was dangerous," said security analyst Charles Shoebridge, calling the attack "one of the most serious security breaches of the past decade."
He said the royal couple should have taken a different route to the theater, or waited until the streets were safe and clear of protesters, or simply sent their regrets and canceled.
"The best means of preventing a subject being attacked is to keep him out of harm's way in the first place," he said.
British police should have been talking with the royal protection squad to ensure the couple never came near the protests -- and most certainly not in a 1977 Rolls-Royce, said Alex Bomberg, a former aide to the royal family and now CEO of a private security firm.
The prince's oversized luxury car lacked speed and maneuverability, and its large clear windows -- with reinforced but not bulletproof glass -- meant Charles and Camilla were clearly visible inside. With two police motorcycles in front and an official royal Jaguar behind it, the vehicle was instantly recognizable as a royal car.
"You couldn't get away in an emergency in a vintage 1977 Rolls-Royce," Bomberg said. "They should have used something more high-powered and up-to-date."
Somehow, protesters also managed to get between the police escort and the royal car.
London's theater district is a maze of narrow one-way streets and constantly crowded with tourists and theatergoers. Cars and taxis making their way through the area often crawl at a snail's pace -- providing an easy target even for attackers on foot.
Without a clear escape route, the vehicle and route should never have been used, Bomberg said.
"You can't blame the royal protection squad for a bunch of anarchists' bad behavior," Bomberg said. "But you can blame someone for not doing their job correctly and not understanding the situation as it was unfolding. Someone's head should bloody roll."
Police, using live video feeds, should have kept the royal protection squad appraised of the volatile situation and been ready to change plans at a moment's notice, Bomberg said.
Metropolitan Police chief Paul Stephenson said the route was checked in advance, "including up to several minutes beforehand, when the route was still clear."
"I do think that the officers who were protecting their royal highnesses showed very real restraint. Some of those officers were armed," he said.
Police would not comment on how close armed royal protection officers came to drawing their guns.
The Metropolitan Police said it had launched a "major criminal investigation," focused on who was behind Thursday's violence.
Given the number of world leaders, royals, celebrities and tourists expected to descend on London for this spring's royal wedding, Shoebridge said the inquiry needs to be speedy so changes can be immediately put in place.
"If there is to be any silver lining, it would be that this incident provides a wake-up call to Scotland Yard to learn from this and ensure that the royal wedding passes off trouble-free," he told the AP.
There have been other royal security breaches. Princess Anne escaped a kidnapping attempt in 1974, and in 1981 six blank rounds were fired at Queen Elizabeth II as she rode on horseback. In 1982 the queen woke up to find a strange man sitting on her bed in Buckingham Palace but safely summoned security.
In 1994 a student charged at Charles while firing a starting pistol during a ceremony in Sydney, Australia, and a comedian dressed as Osama bin Laden crashed Prince William's 21st birthday party at Windsor Castle in 2003.
In the end, Thursday's fiasco seemed to come down to the royal convoy getting stuck in the wrong place at the wrong time.
The protesters, many wearing hooded sweat shirts, their faces hidden by scarves or balaclavas, had broken off from a large demonstration against university tuition hikes that was being contained by police outside Parliament.
The group headed northwest into the West End, a busy shopping and nightlife district, where the mob smashed shop windows, including those of a Starbucks, and overturned postcard stalls.
At the same time, the royal entourage was heading east from Clarence House, Charles' London home near Buckingham Palace, to the Palladium theater on the West End.
The two groups met in Regent Street, home to glossy shops including the Apple Store and Hamley's toy shop.
After the attack, the royal car continued on to the Palladium, where Charles and Camilla attended a charity performance featuring Australian pop performer Kylie Minogue, the British band Take That and singing sensation Susan Boyle.
Asked how she was after the show, Camilla was quoted as saying on the prince's website: "I'm fine thanks -- first time for everything."