Mr Lownie accused Southampton University of ignoring him and his lawyers in their quest to gain access to the material, believing they “could get away with it”.

“This material was bought by the university to be made available, and it failed to do so – and I think that is a shameful thing,” he said.

He insisted he had “no problem” with the Royal family’s right to privacy but added that there should be a balance because they were public servants and legitimate subjects of investigation.

“I don’t think that, in terms of what I’m seeking, there is no material that is sensational or embarrassing,” he said. “There are legitimate reasons to keep information secret about the conduct of the Royal family to preserve the dignity of the Crown, but one has to keep things in perspective.”

He said that, within a week of being sent some of the documents, he managed to ascertain that much of the redacted material was already in the public domain, in books and biographies, which “rather makes a joke of the whole thing”.

Mr Lownie insisted he was not a “muckraker journalist” but rather that the case represented important principles about academic freedoms. “A university should be supporting this principle, not trying to suppress it,” he said.

Roger Smethurst, the head of knowledge and information management at the Cabinet Office, said the material could impact the “dignity” of the Queen.

“Protection of the dignity of the person of the sovereign includes protecting Her Majesty’s privacy and the privacy of members of the Royal Family, where their personal lives might have an impact upon that dignity,” he said in a witness statement.

“Despite its age, there is some information within the documents held by the university which, if released, would compromise the UK’s relations with other states.”

The hearing continues.