Queen Camilla has cancelled all of her engagements this week after falling unwell with a chest infection, Buckingham Palace has announced.
The 77-year-old, who has not long returned from a busy official overseas tour to Australia and Samoa, is understood to be resting at home.
On Tuesday afternoon, a Palace spokesperson 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.
"She apologises to all those who may be inconvenienced or disappointed as a result."
The Duchess of Gloucester has stepped in on the Queen's behalf to attend the annual opening of the Field of Remembrance at Westminster Abbey on Thursday.
Queen Camilla has also pulled out of a Buckingham Palace reception for Olympic and Paralympic athletes hosted by the King the same evening.
It is understood the Queen is currently resting at home. No further details regarding her illness or treatment have been released but she is understood to be under doctors’ supervision.
Prime Minister Sir Keir Starmer posted a get-well message to the Queen on social media. Sir Keir wrote: "On behalf of the whole country, I wish Her Majesty The Queen a speedy recovery."
The chest infection comes shortly after the King and Queen enjoyed a spa break in India en route to the UK from their ten-day tour of Australia and Samoa.
A spokesperson for Buckingham Palace confirmed that Their Majesties had a short, private stopover in India to help break the long journey back from Samoa.
LISTEN: A closer look at King Charles and Queen Camilla's tour in Australia
After their tour, a palace official revealed that the King "genuinely loved" the tour and "genuinely thrived" on the Australian and Samoan programme, adding that the trip lifted “his spirits, his mood and his recovery.
"In that sense, the tour, despite its demands, has been the perfect tonic". He went on to say the monarch took great strength from the Queen being there, not least because she "keeps it real".
Charles temporarily paused his cancer treatment while on the long-haul trip, but it's been confirmed that more overseas visits are planned for next year as he manages the disease.