The Prince of Wales and the Duchess of Cornwall came under attack in London on Thursday evening when their car was caught up in the student riots.
Charles and Camilla's Rolls Royce had just turned into Regent Street on their way to the Royal Variety Performance when around 20 demonstrators threw paint and bottles over the car and shattered a back window.
While visibly shaken, the couple were left "unharmed" and continued on to their engagement, a Clarence House spokesperson said.
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The incident took place as the latest demonstrations against a raise in tuition fees in England descended into violence and vandalism, leaving ten police officers injured and 34 people arrested.
Benches were set fire to in Parliament Square and windows smashed at the treasury as protestors made their way down Oxford Street.
With questions raised about royal security and police handling of the protests, Prime Minister David Cameron condemned the attack as "shocking and regrettable".
And Metropolitan police chief Sir Paul Stephenson voiced his anger, saying: "Right-minded people, including peaceful protestors who wanted to make their point, will condemn what we saw today."
Matthew Maclachlan, who witnessed the attack, told the Daily Telegraph: "The police cars at the front of the convoy drove straight into the crowds at the top of Regent Street.
"They got trapped in that mob and it meant that Charles and Camilla were on their own further down the road except for a Jaguar travelling behind them.
"Charles and Camilla's car ran into such a concentration of people that it had to stop. It was stationary for a lot of the time, then it would squeeze forward an inch. They had just one bodyguard in the car with them and a chauffeur.
"It must have been frightening for them but, throughout it all, Charles was really calm and smiling at everyone. Camilla was beaming too. He was holding out his hands towards them in a gesture that said, 'I'm innocent'."