Queen Elizabeth has been advised by her doctors to rest for at least the next two weeks, avoiding official visits and only undertaking desk-based duties during this time, palace officials say.
The Queen, 95, will not attend a festival of remembrance scheduled for 13 November but has a "firm intention" to be present at a service of remembrance for military veterans on 14 November, the palace added.
The monarch had already pulled out of addressing world leaders in person at the COP26 summit in Glasgow next week, but a palace source said she remained in good spirits and recorded a video address for COP delegates on Friday afternoon.
Further rest for the Queen was "a sensible precaution," the source added.
The Queen appeared in a cheerful mood in video footage released by the palace on Thursday, when she took part in a ceremony awarding a medal for poetry.
She has also been shown accepting credentials from foreign ambassadors via video link.
