Prince Charles and the Duchess were unharmed as the window of the Jaguar was smashed and the car was covered in paint.
An eyewitness said the couple became separated from their police escort as they drove up Regent Street towards the London Palladium, and found themselves in the midst of crowds who had just left the protest in Trafalgar Square. Protesters bombarded the car with bottles and bins.
Nine police officers have been seriously injured in the violence and a number of protesters have attempted to storm the Treasury building. MPs voted 323 votes to 302, a majority of 21 in favour of the motion despite vocal opposition from some Liberal Democrats and a handful of Tory MPs.
Vince Cable, the Business Secretary, said he was "proud" of the Government's package, which will allow English universities to treble fees from 2012.
Mr Cable, a Liberal Democrat, insisted the plan was "progressive" and would "maintain high quality universities in the long term".
Flanked by David Cameron, the Prime Minister and his deputy, Nick Clegg, Mr Cable faced angry cries from Labour backbenchers as he insisted the plans were "more progressive".
He said: "I don't pretend, none of us pretend, that this is an easy subject. Of course it isn't. We have had to make very difficult choices.
"We could have made a decision to d [...]
