Rampaging protesters attacked a car containing the Prince of Wales and the Duchess of Cornwall as the latest tuition fees demonstration descended into vandalism and violence.
Charles and Camilla were visibly shaken but unharmed after their armoured limousine was set upon by an angry mob as the royal couple made their way to an engagement in central London.
The car was kicked, daubed in paint and a rear window shattered as trouble spread across the capital after MPs voted to almost triple tuition fees up to 9,000.
With questions about royal security being raised, Prime Minister David Cameron condemned the attack as "shocking and regrettable" and said the protesters would "face the full force of the law".
The Metropolitan Police was also facing questions about its operation after large parts of the capital became a battleground, forcing another huge clear-up operation today.
Benches were set alight in Parliament Square, Winston Churchill's statue was vandalised, windows smashed at the Treasury and the Supreme Court and protesters rampaged up Oxford Street.
Students hurled missiles at lines of heavily armed police who responded by striking protesters with batons and charging them on horseback.
Television pictures showed demonstrators lying bloodied and battered on the pavements while other images revealed injured police officers being helped by concerned colleagues.
Police said 12 officers and 43 protesters were injured, while at least 26 arrests were made.
Charles and Camilla's car was attacked as it was driven down Regent Street.
Up to 20 demonstrators set upon the vehicle with fists, boots and bottles, chanting "Off with their heads!" and "Tory scum".
One witness said Charles kept calm, gently pushing his wife towards the floor to get her out of the line of fire.
"Charles got her on the floor and put his hands on her," said Adnan
Nazir, a 23-year-old podiatrist who was following the protesters.
Camilla later joked about the incident, saying "First time for everything" while leaving the Royal Variety Performance at the London Palladium.
She and Charles were flanked by their protection officers and uniformed police as they stepped into the back of a waiting police vehicle.
The Met refused to be drawn when asked if an internal investigation would now be launched regarding the incident, but the attack is bound to raise questions regarding royal security.
Tory MP Mark Pritchard, member for The Wrekin in Shropshire, said: "If (the police) knew what was going on, why did they allow the royal convoy to go down that route?"
Home Secretary Theresa May added that the "next steps" in relation to the attack on the royal car were down to the force.
The violence came during the third protest in response to the coalition Government's plans to raise tuition fees.
Police lost control of the first march last month when protesters stormed the Millbank Tower in central London. But yesterday's violence was on a greater scale.
The trouble intensified after MPs voted by a majority of 21 to hike fees up to 9,000. Protesters shouted "shame on you" as news of the result filtered out to the crowd.
Met Police Commissioner Sir Paul Stephenson described yesterday as a "very stretching day" for the force and a "very disappointing day" for London.
He said: "We did everything we could to facilitate peaceful protest and, in reality, whilst I'm sure the vast majority came here to want to protest peacefully, a significant number of people behaved very badly today.
"We want to see people peacefully protesting on the streets of London if that's what they wish to do, but the behaviour today is wholly unacceptable and we will now mount a very serious and very detailed investigation to try and identify the perpetrators of the violence today."
Students marched from universities and colleges across London to protest against the rise, converging on Trafalgar Square at lunchtime.
At 1.30pm they started walking quickly away from Trafalgar Square, down the Mall, towards Buckingham Palace.
Police said the Christmas tree in the square was set alight by protesters, and one demonstrator was seen swinging from a Union flag attached to the Cenotaph.
Hundreds of armed police were waiting for the protesters in Parliament which was barricaded by a double row of steel barriers.
The march was expected to carry on to Victoria Embankment but a large number of protesters remained in Parliament Square.
A number of benches were set ablaze as demonstrators fought running battles with police at the Victoria Street entrance to the square.
Missiles were hurled at officers and statues were vandalised, including that of Winston Churchill.
After MPs passed the vote, protesters set alight a discarded maintenance shed.
Demonstrators also targeted the Treasury, trying to gain access to the building by smashing windows.
After being denied entry, they moved to the Supreme Court, where they could be seen smashing windows with shovels.
Other protesters later rampaged down Oxford Street, targeting a number of shops as they made their way down the shopping thoroughfare.
Officers corralled demonstrators from Whitehall and Parliament Square onto Westminster Bridge and allowed people to leave in dribs and drabs. Police eventually cleared the bridge around midnight.
The Government's measures will see fees rising to an upper limit of 9,000 a year - with requirements for universities to protect access for poorer students if they charge more than 6,000 per year.
The coalition suffered three resignations and 21 Liberal Democrats defied desperate pleas from leader Nick Clegg and voted against the controversial rise, with eight not voting.