Both Britain and China hailed the four-day visit a success, as Mr Jiang spent the last day touring Cambridge University.

The BBC's Nicholas Witchell: "Some politicians say the policing has been misjudged"

A spokesman for UK Prime Minister Tony Blair said a "new chapter" had been opened in relations with China, while a spokesman for President Jiang said the visit had gone "smoothly".

But human rights campaigners have written to the Metropolitan Police Commissioner, Sir Paul Condon, to complain at the way his officers handled protests.

The Free Tibet Campaign says it has received advice that the European Convention on Human Rights may have been breached during a series of demonstrations in London.

The Cambridge visit came hours after the Prince of Wales provoked excited speculation by declining Mr Jiang's invitation to a state banquet in honour of the Queen.

Demonstrations have accompanied Mr Jiang

Prince Charles is known to be an admirer of the exiled Tibetan leader, the Dalai Lama, who has frequently criticised China's human rights record.

A spokeswoman at Prince Charles' London residence, St James's Palace, said the prince had had a previous engagement and denied the absence was a "snub".

A spokesman for Tony Blair agreed. "Prince Charles went to the state banquet on Tuesday. He was never intended to go last night," he said.

"I am sure President Jiang would not have seen this as a snub in any way, shape or form. We, the Palace and the Chinese are perfectly relaxed about this."

Alison Reynolds, Free Tibet Campaign "Lots of questions to be answered"

However, other experts on royal protocol said that the non-appearance could only be interpreted as a snub.

Harold Brooks-Baker, publishing director of Burke's Peerage, said: "He is expected to do what his mother does politically."

Liberal Democrat peer Lord Avebury, who chairs a parliamentary human rights group, said: "By staying away from the banquet, he signals his displeasure in the only way that is open to him."

Some protesters resorted to climbing trees

There was immediate criticism of the way police handled the hundreds of protesters who greeted President Jiang in Cambridge.

Cambridgeshire police had said they were happy for peaceful demonstrations to take place.

But shortly before President Jiang was scheduled to arrive, police parked three white Transit vans in front of protesters in an apparently deliberate attempt to screen them from the President.

A spokeswoman for Cambridge University said it was considering taking up the matter with the police.

"We think it is very important that people are allowed to make their protests and we were keen for a site to be set aside specifically to allow that," she said.

Sir Percy Craddock, former British Ambassador to China "Human rights is only one strand"

"I don't know whether we will be taking this up with the police or not."

However, a Cambridgeshire police spokeswoman defended the officers involved, saying: "They were just responding to the ever-changing situation."

Not all the protesters were anti-Jiang. Many of the several hundred Chinese students at the university waved banners welcoming their president to the city.

Banquet: "No snub" from Charles

During the Cambridge visit, President Jiang spoke to a selected audience of university academics, students and dignitaries, including former Foreign Secretary Douglas Hurd.

He spoke of the difficulties China had experienced in the 20th century and of his hopes for the future, touching on human rights and the need to respect diversities of cultures.

"In today's China, which is a large and developing country with a population of over 1.2bn, top priority should be given to ensuring the greatest possible majority of its people the rights to subsistence and development," he said. "Otherwise there would be no other right to speak of.

"To ensure our people these rights is in itself a major contribution to the progress of the world human rights cause.

"Collective and individual human rights have to go hand in hand and their co-ordinated development should be pursued, so do economic, social and cultural rights on the one hand and civil and political rights on the other.

President Jiang: Next stop, France

"This is in keeping with China's specific national conditions and is therefore the only way to progress in the human rights cause in China."

President Jiang and his wife, Madame Wang Yeping, have now flown to France for the next stop on their two-week, six-nation tour which also takes in Portugal, Morocco, Algeria and Saudi Arabia.

However, it seems unlikely that this will spell an end to the protests dogging Mr Jiang.