Prime Minister David Cameron has condemned the attacks on Charles and Camilla as "shocking and regrettable" and said the protesters would "face the full force of the law".

Student fees protesters in Regent Street attacked the royal limousine as it was making its way to the Royal Variety Performance.

Serious questions are being asked about the failings in the operation since the car was guarded by royal protection officers.

Sir Paul Stephenson, the Scotland Yard Commissioner, promised a "thorough investigation" into the incident, describing it as "hugely regrettable".

He added: "This is not the fault of the police. This was the fault of the people who tried to smash up that car.

"Let's be very clear where responsibility lies. Responsibility for smashing property, for violence, lies with the people that perpetrate that violence and I want to see them arrested and punished in the correct way."

Camilla later joked about the incident, saying there was a "first time for everything".

Police said 12 officers and 43 protesters were injured, while at least 26 arrests were made.