The Queen will not attend the traditional Braemar Gathering in Scotland this weekend, Buckingham Palace has confirmed.
The Prince of Wales will attend the gathering - the most famous event in the Highland Games - in his mother's place.
A royal source said: “The decision has been made for The Queen's comfort.”
Visitors will enjoy pipe bands, Highland dancing, tug of war matches and hill races during the Braemar Gathering.
It comes after the monarch announced she would not travel to London to bid a formal farewell to outgoing Prime Minister Boris Johnson next week.
The 96-year-old will receive the ousted PM at Balmoral Castle in Scotland instead, it has been announced, as ongoing concerns over her health continue.
His visit will shortly be followed by an audience with Britain's new Prime Minister, a Buckingham Palace spokesperson said.
Her Majesty will welcome either Rishi Sunak or Liz Truss, who are nearing the end of their battle to become the next Tory leader.
The ceremony will mark the first time a new premier has been appointed away from Buckingham Palace during the Queen's 70-year reign.
The last PM to be appointed away from Buckingham Palace came more than a century ago, with King Edward VII asking Herbert Henry Asquith to form a Government in Biarritz, on France’s Basque coast in 1908.
The Queen will greet the new leader on September 6 as Mr Johnson - deposed after a massive Tory revolt last month - hands back the keys to No10.
It will take place at her residence in the Scottish Highlands, where she is on her traditional summer break.
The Queen is reportedly "resting" a lot more following a "change" in her mobility as royal family members visit the monarch at Balmoral.
Her Majesty was last seen publicly on July 21 when she arrived at Aberdeen airport as part of her annual summer holiday to Balmoral, where she traditionally stays between July and October.
Despite her mobility issues, the Queen has been thrilled by visits from her family including "lots of great-grandchildren" spending time with her.
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A source told the Daily Mail that the Queen's mobility has taken "a change in the past few weeks".
The source added: "The Queen’s condition is not what you would call ideal, but then Her Majesty is 96 after all."
Royal experts say Prince Charles' visits to see his mum are a sign he is concerned about her welfare.
Her Majesty was seen for the first time using a walking stick in public earlier this year.
