Comes just weeks after a nine-day tour of Australia and Samoa.

The Queen has been forced to withdraw from all engagements this week after falling ill with a chest infection.

Buckingham Palace said Camilla, who has recently returned from a busy official overseas tour to Australia and Samoa, has been advised to undergo a “short period of rest” by doctors.

A Buckingham Palace spokesperson said: “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 update comes after a year of difficult health troubles for the royal family, with both the King and the Princess of Wales being diagnosed with cancer.

No further details regarding her illness or treatment have been released, but she is understood to be being cared for under doctors’ supervision.