UK to probe lapse in royal security after London riot

British police promised an investigation on Friday after prince Charles, the heir to the throne, was caught up in London's worst riots in years as student protests over a rise in fees boiled over.

Student leaders called for more demonstrations even though parliament narrowly passed the controversial increase on Thursday in a vote which divided Britain's coalition government.

This was the first serious test of the coalition's determination to push through unpopular measures to reduce Britain's record peacetime budget deficit.

The decision to raise the cap on tuition fees almost threefold provoked a serious rebellion among legislators for the centre-left Liberal Democrats, the smaller coalition partner, but Lib Dem business secretary Vince Cable said the government would emerge stronger.

Prime Minister David Cameron condemned the violence and expressed concern about a serious lapse in royal security which allowed a limousine carrying prince Charles, queen Elizabeth's oldest son, and his wife Camilla to be surrounded by protesters.

Their car was spattered with paint and a window was cracked, but the couple were unhurt, though clearly alarmed.

London police chief Paul Stephenson "will be looking into what happened on the streets of London and he will also be looking into specifically what happened with the prince of Wales (Charles)," Cameron said outside his Downing Street residence.

"We do need to learn the lessons of this. It was a very regrettable incident," he said.

Cameron said a significant number of demonstrators were bent on violence and destroying property and the "full force of the law" would be brought down on them.

Tens of thousands of protesters took to the capital's streets on Thursday, in the latest of a series of protests. Protesters clashed with riot police, laid siege to the finance ministry and broke windows.

At least eight police officers and 13 protesters were injured and 34 protesters were arrested, police said.

Analysts say the seven-month-old coalition will hold together, but could come under increasing strain as cuts bite harder next year.

Stephenson said police had checked the route minutes before the royal couple arrived but the situation had changed quickly.

"I do think that the officers who were protecting their royal highnesses showed a very real restraint. Some of those officers were armed," he told the BBC.

He promised a "full criminal investigation" into what he called a "hugely shocking incident" as well as investigations of crimes by protesters and any complaints against police.

Dai Davies, a former head of royal protection, said the royal incident was embarrassing for the police.

"I'm surprised and clearly the (police) commissioner is embarrassed and surprised also why there isn't better coordination," he said.

Clare Solomon, president of the University of London Union, blamed the trouble on provocation by "a violent minority within the police force".

"This will only continue if the government continues the cuts to education, but also to the public services, to housing to pensions," she told the BBC.

London student Stephanie Jones, 17, said after Thursday's vote that students would fight until they won. "We won't stop. The protests are going to get worse -- more action, more fighting," Jones said.