The Prime Minister's surprise statement began: "On my recommendation, Her Majesty the Queen has amended the Letters Patent constituting the Order of Australia."

Letters Patent are the official instrument, the parchment signed by the Queen's own hand with her distinctive "Elizabeth R", that give force to her decisions.

But, mysteriously, although they are public documents published in the Government Gazette, no one has been able to provide evidence that one was signed.

Or show that the Queen had signed the parchment at the time of the Prime Minister's declaration.

This raises an awkward question. When Mr Abbott publicly pronounced Ms Bryce a dame in time for her official reception on March 25, was she? General Cosgrove started using the title Sir on March 28 after his swearing-in as Governor-General, but again was he officially allowed to claim that title?

After repeated requests over several days, neither the Prime Minister's office nor Buckingham Palace would give Fairfax Media the exact date on which the monarch signed the official instrument.

On Wednesday afternoon - after Fairfax Media published this story online - a spokeswoman for the Prime Minister said "the documents" had been signed by the Queen on March 19.

But the Prime Minister's office continued to refuse to release the signed parchment, saying the Letters Patent, which are public documents, would be published "in due course".

Government House was unable to shed any light on the mystery. An official said Government House had not seen the Letters Patent or any copy of them.

The spokeswoman had earlier said that an "electronic version" had been sent and signed in mid-March and that the signing of the paper version was "under way".

However, there is no electronic version of Letters Patent, according to people familiar with Palace workings, and only the parchment bearing the monarch's signature has any force.

An email exchange, in other words, may be no substitute, nor carry any official weight.

However, a former official secretary to successive Australian governors-general, Sir David Smith, said that the standing of electronic versions of Letters Patent would be a decision for the Queen: "If the Queen was prepared to receive an electronic recommendation and send back an electronic copy . . . it must be OK. It has to be."

A Buckingham Palace spokesman would not confirm when Her Majesty had received the Letters Patent from Mr Abbott or whether she had signed it before the Prime Minister's announcement.

"All correspondence between the Queen and her prime ministers and governments is treated in a confidential way by Buckingham Palace," the royal spokesman said.

"Buckingham Palace is not able to confirm signature of any Letters Patent, however, there is no objection if the Prime Minister's Office or Australian Parliament wish to confirm the date, when this is known."

Asked why he had "blindsided" colleagues by announcing knights and dames without informing his cabinet or party room, Mr Abbott stressed the importance of observing proper protocol in his dealings with Her Majesty the Queen.

"In the end the relationship between the prime minister and the monarch is very much a personal one," Mr Abbott told The Conversation website on Friday.

"When it comes to the constitution of the Order of Australia, which is headed by the monarch, this is governed by Letters Patent, which are a matter between the prime minister and the monarchy.

"I think the prime minister is entitled to make these sorts of decisions with the monarch."

As a former director of Australians for Constitutional Monarchy, Mr Abbott has spoken often of the respect required to properly honour Australia's relationship with the Crown.

Mr Abbott has expressed this respect for the Crown consistently throughout his career.

In 2008 he told a gathering of young monarchists: "To me, supporting the monarchy is as natural as respecting your parents".

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