Questions are being raised about security measures for Prince Charles and his wife Camilla after their car was attacked by protesters in London.
The protesters kicked, threw paint and smashed a window of the car which was travelling in central London where there have been violent demonstrations after MPs voted to raise university tuition fees on Thursday.
Protesters battled with police in Parliament Square and hundreds were contained on Westminster Bridge for a time by officers, the BBC reports.
Windows in London's main shopping district were smashed.
Police say 12 officers and 43 protesters have been injured, while 22 arrests were made.
Prince Charles and the Duchess of Cornwall were on their way to attend the Royal Variety Performance and as usual were travelling with their security detail and police outriders.
The couple were unhurt in the incident and attended the event at the London Palladium as scheduled, but later left the theatre in a police van.
Prime Minister David Cameron said the attack was shocking and regrettable and those who provoked the violence will face the full force of the law.
Metropolitan Police Commissioner Sir Paul Stephenson said there would be a "very serious and very detailed investigation" into the disturbances.
A source at Scotland Yard told the BBC police would never put the Royal Family at risk and that the plan had never been for their route to converge with the demonstration. The problem arose when some of those split off from the main protest.
University fees to treble
The vote on Thursday will mean university fees will almost treble to £9,000 a year.
The government's majority was cut by three-quarters to 21 in a backbench rebellion. Three ministerial aides resigned.
Only 28 Liberal Democrat MPs - less than half - voted for the government's plans for tuition fees. Six Conservative MPs voted against.
