British police officials vowed to investigate how tuition hike protesters were able to "smash up" a Rolls-Royce transporting Prince Charles and his wife, Camilla, on Thursday night.

The attack following a controversial vote in Parliament approving an increase in university tuition fees left the couple's vehicle splattered with white paint and a rear window cracked.

Britain's Prince Charles and his wife, Camilla, react as their car is attacked in London on Thursday amid tuition hike protests. (Matt Dunham/Associated Press)

British Prime Minister David Cameron defended the police on Friday, although he conceded there were lessons to be learned from a "regrettable lapse in security."

Speaking from Downing Street, he reminded the public that blame should fall on the violent demonstrators.

"Let's remember that this was not the fault of the police. This was the fault of the people who tried to smash up that car," he said. "Let's be very clear about 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."

'Wrong car to use that night'

Although visibly shaken, the Prince of Wales and Duchess of Cornwall were not harmed as their limousine rolled through the protests in London's bustling West End.

Reports said the car was set upon by as many as 20 protesters, who kicked the car and taunted the couple as they tried to proceed to an evening function.

At least 43 protesters were injured and a dozen police officers were hurt in the fracas, which saw demonstrators hurling flares and billiards balls and riot police responding with smoke bombs. More than 30 people were arrested.

Dickie Arbiter, a former press secretary to Queen Elizabeth and a royals commentator, told CBC News from London that in his assessment, blame on the close encounter with demonstrators falls on the police.

'It was really not so much an attack on the royals, but an attack on the government, and it just so happens that there was a royal car there, and they were using it to vent their anger.'—Dickie Arbiter, royals commentator

"They knew the demonstration was taking place at Parliament Square. They knew it had filtered off into Trafalgar Square half a mile[nearly a kilometre] away," he said, suggesting the areas should have been better secured.

The other problem, he noted, was that the low wheel-based Rolls-Royce — typically a ceremonial car — was not adequate for protecting the passengers.

"Clearly the wrong car to use that night," Arbiter said, adding that an easier route to get to the couple's destination would have involved tight turns.

"This particular car used last night just does not have the turning circle to be able to negotiate those corners, so they should have used an alternative car. But they didn't, and that's what happened."

As for whether taunts of "Off with their heads" seemed to be genuine threats against the prince and his wife, Arbiter said it was not worrisome, and that protesters were just caught up in a volatile situation.

"It was really not so much an attack on the royals, but an attack on the government, and it just so happens that there was a royal car there, and they were using it to vent their anger."

With files from The Associated Press