Britain's Queen Elizabeth, the world's longest-reigning monarch, cancelled a planned visit to Northern Ireland on Wednesday and accepted medical advice to rest for the next few days, Buckingham Palace said.
The queen, 95, has reigned for almost seven decades. She was just 25 when she became Queen Elizabeth II on Feb. 6, 1952 on the death of her father.
"The queen has reluctantly accepted medical advice to rest for the next few days," the palace said.
"Her Majesty is in good spirits and is disappointed that she will no longer be able to visit Northern Ireland, where she had been due to undertake a series of engagements today and tomorrow."
A source said the queen's decision was not related to Covid.
The queen sent her "warmest good wishes to the people of Northern Ireland, and looks forward to visiting in the future", the palace said.
Just this week, Elizabeth brushed aside an attempt by a magazine to award her the title of "Oldie of the Year", saying that she felt too young at heart.