King Charles III will be proclaimed Canada's new head of state at an accession ceremony at Rideau Hall on Saturday morning, while the federal government rolls out a series of events to commemorate the legacy of his mother, Queen Elizabeth II.

The date of Canada’s national commemoration ceremony for the Queen is up in the air as officials eagerly await public confirmation of when her state funeral will be held in London.

The Heritage Department says the national ceremony will start with a memorial parade composed of Canadian Armed Forces members and RCMP officers along with a 96-gun salute — one for each year of her life — and a CF-18 flypast.

That will be followed by a service at the Anglican Christ Church Cathedral in downtown Ottawa, which will be attended by government officials and other dignitaries and nationally televised for all Canadians.

While planning for the actual ceremony has been underway for years, Beth Bretzlaff, rector of Christ Church Cathedral and dean of the Anglican diocese of Ottawa, said the devil is in the details. And the biggest missing detail now is the date.

"We don't know when it is in England yet," Bretzlaff said in an interview. "So it's all kind of resting on them."

Protocol calls for 10 days of mourning following the Queen's death, but the rules around the actual funeral are not as rigid. British officials are expected to announce the date in short order.

The longest-serving British monarch and Canadian head of state died Thursday. 

Despite the uncertainty, Bretzlaff said preparations are proceeding. 

“There's a lot of details, specifically around components of the service,” she said. “Who is doing what and how people line up and where they go and who sits where .… You've also got the music, and all the people who may be participating, let alone the guests.”

Christ Church is not new to such ceremonies; it hosted a similar national commemoration for the Queen’s late husband, Prince Philip, last year and another for the Queen Mother in 2002.

Queen Elizabeth and Prince Philip actually worshipped at the 750-seat cathedral on two occasions in 1957 and 1961. 

“And on one of those occasions, the power went out,” Bretzlaff said. “The service continued on, but there was no organ. They sang without music and lit the candles. It was rather an intimate relationship with the Queen herself in this place.”

Prime Minister Justin Trudeau is scheduled to meet with his cabinet on Saturday morning before heading to Rideau Hall to join Gov. Gen. Mary Simon at the proclamation ceremony. He is also expected to attend the state funeral in London.

Late Friday, following his return from a three-day cabinet retreat in Vancouver, Trudeau arrived at Rideau Hall to sign a book of condolences for the Queen.

"In this moment, all Canadians are joined in grief. Canada came of age during Her Majesty Queen Elizabeth's time as Sovereign, and generations of us have benefitted, profoundly, from her steady, graceful leadership and service," the prime minister wrote.

The book of condolences at Rideau Hall is available to Canadians mourning the Queen's death, and an online version is available from Canadian Heritage.

This report by The Canadian Press was first published Sept. 9, 2022.