British police began a wide-reaching probe Saturday into a recent wave of student protests, after the latest culminated in a mob attack on a car carrying Prince Charles and his wife Camilla.
Prime Minister David Cameron said he was "very concerned" by the royal security lapse, which occurred Thursday during the most violent of a string of protests against his coalition government's plans to raise university fees.
Charles, the heir to the throne, and his wife looked shocked as rampaging demonstrators broke a window of their Rolls Royce and spattered the car with paint.
They intercepted the car as the couple travelled to a theatre in London's West End.
At the same time, across the city in Westminster, thousands of angry youths clashed with riot police and tried to storm the finance ministry after the government narrowly won a parliamentary vote on raising university fees.
Clarence House, the royal couple's official residence, would not comment on newspaper reports that Camilla had been hit in the ribs by a stick shoved through one of the car windows which was accidentally opened in the melee.
"But what we are saying is that both their royal highnesses were unharmed and neither received any medical attention," a spokesman told AFP Friday.
Cameron said those who attacked the car had to be punished.
"We want to learn the lessons from that but, above all, we want to make sure that the people who behaved in these appalling ways feel the full force of the law of the land," he said.
Scotland Yard chief Paul Stephenson said the couple's route had been thoroughly surveyed minutes before the attack, adding that armed protection officers had held back by not opening fire on protesters.
"I do think that the officers who were protecting their royal highnesses showed very real restraint, some of those officers were armed," he told BBC radio.
"But it was a hugely shocking incident and there will be a full criminal investigation into it."
Police later announced a major investigation into all student protests in the capital since the first day of action against the fees increase on November 10, when rioters attacked Cameron's Conservative party headquarters.
"We support the public's democratic right to peacefully protest," a spokesman said, but violence "will not be tolerated", he added.
Clarence House said Charles and Camilla were "grateful" for the police's action, but the incident has raised serious security questions, particularly ahead of the wedding of Charles' son Prince William in April.
The royal couple were targeted by a breakaway group of around 200 protesters chanting "off with their heads" as they drove to a charity concert.
As a smiling Camilla left afterwards, she told reporters: "I'm fine thanks -- first time for everything."
Former royal police officer Charles Shoebridge said the incident "ranks amongst the most serious security breaches of the past decade."
Police arrested 33 people during the protests and at least 43 protesters and 12 police officers were injured during the clashes outside parliament.
A police watchdog launched an investigation after a 20-year-old student needed surgery after allegedly being hit on the head with a police truncheon.
The plans to raise fees led to the first government resignations over policy and exposed deep strains in junior coalition partners the Liberal Democrats, who before the election had pledged to oppose any rise in tuition fees.
The government's majority was cut by three-quarters as lawmakers voted by 323 to 302 to raise the cap on annual tuition fees at English universities from 2012.
As part of widespread austerity measures aimed at cutting Britain's deficit, the basic level of fees will now climb to 6,000 pounds (9,460 dollars, 7,140 euros), with an upper limit of 9,000 pounds.