Queen Camilla has pulled out of a number of scheduled engagements because of a chest infection, says Buckingham Palace.
Doctors have advised a short period of rest at home, but she hopes to be well enough to attend Remembrance events at the weekend, says the Palace.
The Queen, who is 77, will miss the annual opening of the Field of Remembrance at Westminster Abbey on Thursday, where she will be represented by the Duchess of Gloucester.
The Queen returned to the UK last Wednesday after a trip with the King to Australia and Samoa, which included a stopover in India on the way back.
It is understood there is no cause for alarm – and her plans to attend engagements at the weekend suggest a relatively minor bug, of the type which could have been picked up during her long-haul travels.
The Remembrance events at the weekend will include the Festival of Remembrance at the Royal Albert Hall on Saturday and the commemorative service on Sunday morning at the Cenotaph in Whitehall.
But the Queen will not be at the Field of Remembrance commemoration on Thursday, where she has been the senior royal in recent years. Standing in for her will be the Duchess of Gloucester, a working royal, aged 78, who is married to a cousin of the late Queen Elizabeth II.
This annual remembrance event sees people placing memorials outside Westminster Abbey to those who have lost their lives while serving in the armed forces.
The Queen will also miss a Buckingham Palace reception for Olympic and Paralympic athletes, which will be hosted King Charles on Thursday evening.
Prime Minister Sir Keir Starmer wished the Queen a “speed recovery” in a message posted on social media.
A statement from the Palace on the Queen’s health said: “Her Majesty The Queen is currently unwell with a chest infection, for which her doctors have advised a short period of rest.
“With great regret, Her Majesty has therefore had to withdraw from her engagements for this week, but she very much hopes to be recovered in time to attend this weekend’s Remembrance events as normal.”
The Queen previously missed a week of engagements with ill health in February 2023, when she tested positive for Covid. It was the second time she contracted the virus, having previously had it in February 2022.
In recent weeks, the Queen had accompanied the King on a tour of Australia and Samoa, which included a Commonwealth summit. There were reports that she had visited a health spa in India on the way back.
The Queen has also recorded a TV documentary raising awareness about domestic violence, which will be broadcast next week.
King Charles received a cancer diagnosis in February. His treatment was paused during his overseas trip but was expected to begin again on his return to the UK.