• Queen Elizabeth is totally in control of her faculties and everything at the palace
  • Asking Prince Charles and Prince William to attend the State Opening of Parliament showed teamwork
  • Robert Lacey said that the Queen's only problem was her mobility, and it's neither a constitutional or regency issue

Queen Elizabeth remains the head of state, and she's still in control despite making fewer public engagements.

The 96-year-old monarch fueled health concerns when she canceled her attendance at the State Opening of Parliament Monday, just a day before the event. It was the first time she skipped the event in over five decades.

Prince Charles, Camilla Parker Bowles and Prince William attended the event on behalf of the Queen. Royal historian Robert Lacey acknowledged that the Prince of Wales and Duchess of Cornwall's attendance at the opening was an "enormously significant moment." However, he denied the rumors of regency as the Queen's only health problem was her mobility.

"The sense I get from everyone I speak to is that the Queen remains totally in control of her faculties and of everything at the palace," he told People. "The problem is physical mobility — and that is not a constitutional or regency issue. She is in charge."

As for the three senior royals attending the State Opening of Parliament on her behalf, the "Battle of Brothers" author said it was an indication that the Queen was thinking about the future of the monarchy. However, the rumor about regency was out of the question.

"She's clearly thinking of the future and this can be seen alongside the moment she said it was her wish that Camilla be known as Queen Consort, which was another important development this year," the expert added. "Asking her son Charles and William to attend is clearly about succession, about emphasizing a partnership and teamwork."

He noted that regency is when the powers of the sovereign are formally transferred to the heir because the monarch can no longer carry out their duties. Lacey noted that regency "is very much not happening in this case."

Buckingham Palace announced Monday that the Queen would miss the annual occasion due to mobility problems.

"The Queen continues to experience episodic mobility problems, and in consultation with her doctors has reluctantly decided that she will not attend the State Opening of Parliament tomorrow," a statement from Buckingham Palace read Monday, Us Weekly reported. "At Her Majesty’s request, and with the agreement of the relevant authorities, The Prince of Wales will read The Queen’s speech on Her Majesty’s behalf, with The Duke of Cambridge also in attendance."

The Queen won't attend every upcoming event for her Platinum Jubilee for the same reason. Her Majesty has been "having mobility issues and as a result, her diary has been scaled back," an unnamed family source told Entertainment Tonight.

Queen Elizabeth is expected to show up on the balcony for Trooping the Colour. Prince Harry and Meghan Markle confirmed that they would return to the U.K. for the Queen's Jubilee. However, the Duke and Duchess of Sussex won't be making a balcony appearance since the monarch decided to limit the royals accompanying her on the balcony to active working royals, including Prince Charles, Prince William, Duchess Camilla, Kate Middleton and Princess Anne to name a few.

Queen Elizabeth II, 96, last missed a state opening of parliament in 1963, when she was pregnant with Prince Edward
Queen Elizabeth II, 96, last missed a state opening of parliament in 1963, when she was pregnant with Prince Edward POOL via AFP / Dominic Lipinski