(CNN)Britain's Queen Elizabeth II missed the Remembrance Sunday service in central London after spraining her back, Buckingham Palace said Sunday.
"The Queen, having sprained her back, has decided this morning with great regret that she will not be able to attend today's Remembrance Sunday Service at the Cenotaph. Her Majesty is disappointed that she will miss the service," a statement said.
Prince Charles laid a wreath at the Cenotaph on the Queen's behalf, as in previous years.
Buckingham Palace had confirmed on Thursday that the 95-year-old monarch was well enough to attend the ceremony to commemorate those who have died in conflicts.
Queen Elizabeth's decision to pull out of the Remembrance Day Sunday service after spraining her back is unrelated to her doctor's recent advice to rest, according to a royal source.
The timing is unfortunate and nobody regrets the Queen's absence today more deeply than the monarch herself, the royal source told CNN.
The source also said that the Queen was deeply disappointed to miss the engagement, and that she considers it one of the most significant engagements of the year.
British Prime Minister Boris Johnson on Sunday volunteered that the Queen was "very well" when he saw her last week.
"I know that everybody will be wanting to offer their best wishes to her majesty the Queen and I just wanted to reassure everybody by saying that I did see the Queen for an audience last week on Wednesday in Windsor, and she's very well," Johnson said at the end of a press conference marking the conclusion of the COP26 summit.
"It shouldn't need saying but I just wanted to say it anyway," he said.
Several other members of the royal family, including Camilla, the Duchess of Cornwall, and William and Catherine, the Duke and Duchess of Cambridge, attended the Remembrance Sunday service as planned.
Large crowds gathered around the Cenotaph this Sunday after the annual service was largely curtailed by Covid-19 restrictions last year.
It has been more than three weeks since the Queen attended a public event -- when she hosted a reception for business leaders at Buckingham Palace ahead of the COP26 climate conference in Glasgow.
The day after, the sovereign abruptly canceled an imminent trip to Northern Ireland and spent a night in hospital for what a spokesman described at the time as "preliminary investigations."
Since then and following her doctor's orders, the royal household has scaled back her diary significantly. She has been mostly resting at Windsor, undertaking a few light duties by video link and phone.
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