The solemn appointment will be special this year.
Queen Elizabeth II will be absent on Tuesday for the Speech from the Throne in Parliament, Buckingham Palace announced Monday evening, citing the monarch's "mobility problems".
She will be replaced by Prince Charles.
“The Queen continues to have episodic mobility issues and, after consultation with her doctors, has reluctantly decided not to take part in the Speech from the Throne,” the palace said in a statement.
It is the first time in more than sixty years that the 96-year-old queen – she only missed the appointment twice (1959, 1963) when pregnant during her reign – will not read the speech of the throne, written by the government to outline its priorities.
It is also the first time that Prince Charles, heir to the crown, will replace her.
Only one public appearance for several months
"At Her Majesty's request and with the agreement of the relevant authorities, the Prince of Wales will read the Speech from the Throne on her behalf, with the Duke of Cambridge (Prince William, the Queen's grandson) also present," said the palace.
This absence, the year of the platinum jubilee celebrations for her 70 years on the throne, marks a new symbolic stage in the gradual transfer of the sovereign's tasks to Prince Charles, who has already represented her abroad for several years.
Since a brief hospitalization in October, Elizabeth II's appearances have become extremely rare, although she continues to take on "light duties" at Windsor Castle, mostly by videoconference.
On March 29, however, she attended a religious ceremony in Westminster Abbey in honor of Prince Philip.
It was his first major public appearance in months.
The monarch, seen with a cane in recent months, had herself confided in mid-February that she "could not move", showing her left leg during an audience in Windsor.