Australia’s prime minister Monday defended a long-standing protocol blocking the nation's Parliament from sitting for 15 days following the death of a British monarch.

Lawmakers are expected to reconvene Sept. 23 to debate a condolence motion for Queen Elizabeth, which is the earliest date allowed under the obscure protocol, Prime Minister Anthony Albanese said.

With the last British monarch dying in 1952, the Australian protocol is not well-known. Asked who was behind the protocol, Albanese told reporters it had “been in place for a long period of time.”

“I think there is something to be said for a prime minister who follows tradition, who follows protocols and who follows order,” he said. “That is something that I hope to define my prime ministership is respect for those traditions.”

The king and queen consort have left London for Holyrood in Edinburgh, where they will accompany the queen's coffin in a procession to St. Giles Cathedral. Their plane took off around 11.30 a.m. (6.30 a.m. ET).

The couple will join other members of the royal family, including Elizabeth’s children and grandchildren, walking behind the queen’s coffin on its route to the cathedral, with the guns of Edinburgh Castle firing every minute throughout. Thousands of people are expected to line the Royal Mile to watch.

Charles’ visit to Edinburgh officially marks the start of his tour of all the four nations of the kingdom: England, Scotland, Wales and Northern Ireland.

A service will be held at that cathedral, where the queen’s coffin will rest for 24 hours, allowing members of the public to file past and pay their respects from 5 p.m. (noon ET). The Scottish government has warned that people could be stood waiting for many hours in “potentially challenging weather conditions.”

Prince Louis said the queen was “now with great-grandpa" after learning of her death, his mother told mourners who had gathered in Windsor on Saturday.

“My little Louis, he’s so sweet, he said, ‘Mummy don’t worry, she’s now with great-grandpa’... That just shows you how special she was to everybody, of all generations,” said Kate, the Princess of Wales, according to TikTok footage verified by NBC News.

“Kate was so lovely, kind and concentrated. She was willing to talk to all the public," Nicole Gumienny, a 16-year-old from Farnborough, England, who was present at the meeting, told NBC News.

“My eyes started watering when she mentioned Prince Louis talking about the queen being with great-grandpa now.”

The thanksgiving service to be held for the life of the queen at St Giles' Cathedral in Edinburgh on Monday will be preceded by hymns including "Thou knowest Lord the secrets of our hearts" and "Salvator mundi."

Singer Karen Matheson will sing a psalm in Gaelic and readings will be made by the Archbishop of St Andrews and Edinburgh, Most Rev. Leo Cushley and Most Rev Mark Strange, Bishop of Moray, Ross & Caithness, Primus of the Scottish Episcopal Church.

Prayers will be also read by Morag Mylne, an Elder of the Church of Scotland, and Samuel Nwokoro, a Commonwealth student from Nigeria.

The service will be sung by the cathedral's choir conducted by the Master of the Music Michael Harris, and the organ will be played by Jordan English. The service will conclude with the national anthem “God Save the King.”

King Charles addressed parliament on Monday, saying he was “resolved” to follow his mother’s “example of selfless duty.”

Britain’s new monarch said he was “deeply grateful” for condolences received by lawmakers following his mother’s death. He said the messages of sympathy “so touchingly encompass what our late sovereign, my beloved mother, the queen, meant to us all.”

Of his mother, Charles said: “While very young, her late majesty pledged herself to serve her country and her people and to maintain the precious principles of constitutional government, which lie at the heart of our nation.”

“This vow she kept with unsurpassed devotion,” he said. “She set an example of selfless duty, which ... I am resolved faithfully to follow.”