But this time the inquisition took place, not in Parliament House, but in a Sydney court room.

In a rare return to his pre-political career as a senior barrister, shadow attorney-general Mark Dreyfus, QC, has personally taken the current Attorney-General, George Brandis, to the Administrative Appeals Tribunal over his refusal to release his diary schedule under freedom of information laws.

On Friday, Mr Dreyfus subjected the man who refused the request, Mr Brandis' chief of staff, Paul O'Sullivan, to more than an hour of examination.

Mr O'Sullivan maintained his position that meeting the FOI request, which related to eight months of diary entries in 2013, would have placed an "unreasonable burden" on the Attorney-General and his staff.

He said it could potentially involve consulting the many hundreds of people who had attended appointments to ask whether there was any reason for the meeting to be kept secret.

"Well let's say the Attorney-General spends an hour every morning meeting with paid lobbyists, would they have to be consulted?" Mr Dreyfus asked.

"Quite possibly, yes," Mr O'Sullivan said.

The public servant said that, when this process of consultation was added to the task of redacting irrelevant or exempt material, it would take between 301 and 307 hours.

"There's a complex process to have redactions, because there's only one operator who's properly trained and only one computer has the Adobe Acrobat program," Mr O'Sullivan said

"You seem happy that you don't have to undertake that," Mr Dreyfus replied dryly.

"Well yes, I am," Mr O'Sulivan said.

Mr O'Sullivan also maintained his position that releasing the diary entries could reveal the Attorney-General's movements, creating risks to his safety.

"But, Mr O'Sullivan, we're talking about a single line diary entry that says nothing more than who the Attorney-General actually met with," Mr Dreyfus said.

"There's a thing called the mosaic effect where a pattern of behaviour can be determined," Mr O'Sullivan said.

Mr Dreyfus said that he made the FOI request because a number of the Attorney-General's major policy decisions, including to defund environmental defenders' offices, had been made without consultation and the public needed to know whether he consulted widely or not.

"They have come up with every possible reason and come up with every possible complication," he told the court on Friday.

"They have come up with hundreds of hundreds of hours involved in the handling of the request. It flies in the face of common sense."

"There's been a gross exaggeration in the amount of time that's said to be involved in producing this."

"In essence, we put it that the Attorney-General has entirely taken the wrong approach to the particular refusal reason."

Lawyer Justin Davidson, for Senator Brandis said that the calculations of how much time it would take to process the request were "reasonable".

"Within that spectrum of eight months, 130 people fit into that category of people who would have to be consulted," Mr Davidson said.

"That's not all of them, it's around half."

He said that determining what was in the public interest was a balancing exercise, where the right of the community to information about the Attorney-General needed to be balanced against the right to privacy of the individuals who had met the minister.

The presidential member of the Administrative Appeals Tribunal, Justice Jayne Jagot, has reserved her decision.

Speaking at a Centre for Independent Studies event on Friday, Senator Brandis joked: "I do intend to publish a diary, if only Mr Dreyfus were patient.

"But I hope it will be a diary in the Harold Nicolson, Chips Channon and Alan Clark genre [of English politicians and diarists] ... rather than the dreary appointments diary the shadow attorney-general is seeking to have disclosed.

"Were he to be successful I am sure [it] would contain nothing more interesting than a day-by-day study of the weariness and drudgery of my life."

With Michaela Whitbourn