"We say it is absolutely vital to the position of the claimant, and anyone else in his position, that this sort of document cannot be published willy-nilly by the press," said Hugh Tomlinson QC, on behalf of Prince Charles.
The Prince of Wales claims that eight diaries were copied by a former member of his staff and is suing the Mail on Sunday's owners Associated Newspapers for breach of copyright and confidentiality.
In extracts about the 1997 Hong Kong handover published in the Mail on Sunday last November, the prince described Chinese officials as "appalling old waxworks".
And in another reported extract, Prince Charles described a ceremony as an "awful Soviet-style" performance and called a speech by then-Chinese President Jiang Zemin "propaganda".
As the hearing began, more details of Prince Charles' alleged "disapproval" of the Chinese regime were revealed after Mark Bolland's witness statement was released by the paper and it also said that: "He would readily embrace the political aspects of any contentious issue he was interested in and this is an aspect of his role, which the prince saw as particularly important."
Mr Bolland said the prince's behaviour was controversial because the constitution stops members of the Royal Family from expressing political viewpoints.
He went on to say that Prince Charles later did not attend a state banquet thrown by Chinese President Jiang Zemin "as a deliberate snub".
He added: "He did not approve of the Chinese regime, and is a great supporter of the Dalai Lama, whom he views as being oppressed by the Chinese".
However, the legal team for Prince Charles have denied that he deliberately boycotted the banquet.
Prince Charles says the documents, which include the 3,000-word journal he entitled The Handover of Hong Kong - or The Great Chinese Takeaway, were copied illegally and he wants the court to order them to be returned.
Mr Tomlinson said the Prince of Wales had given copies of his private journals to family members and friends and advisers over the last 30 years in envelopes, which were marked private and confidential.
Prince Charles recognised he was the subject of public comment, Mr Tomlinson told trial judge, Mr Justice Blackburne, at the beginning of the trial.
"What he says, however, is that like everyone else, from the humblest private citizen to the highest public figure, he is entitled to keep his personal documents private," Tomlinson explained.
Mr Tomlinson claimed that the publication of extracts from the journal in the Mail on Sunday could not be justified as "press freedom" as the right of free speech was governed by responsibilities.
Mark Bolland's statement said the prince's "very definite" aim was to influence opinion and that "he saw that as part of the job of the heir apparent," he added.
"He carried it out in a very considered, thoughtful and researched way. He often referred to himself as a 'dissident' working against the prevailing political consensus," Bolland's statement continued.
