Queen Camilla has chest infection: Buckingham Palace

"Her Majesty The Queen is currently unwell with a chest infection, for which her doctors have advised a short period of rest," a 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."

The illness means Camilla, Charles's second wife who he married in 2005, will miss this year's Field of Remembrance event at London's Westminster Abbey on Thursday which allows former service personnel and others to plant a poppy memorial to remember those who have lost their lives in the armed forces.

"She apologises to all those who may be inconvenienced or disappointed as a result," the palace spokesperson said.

Her place will be taken by the Duchess of Gloucester.

The King himself is still undergoing treatment for cancer which was diagnosed back in February, forcing him to cut back on some of his engagements although he recently travelled with Camilla to Australia and Samoa.