The Queen will miss the Braemar Gathering in Scotland, the popular Highland Games event which the Prince of Wales is scheduled to attend on Saturday.
It is understood the decision has been taken for the comfort of the head of state, who has been suffering from mobility problems since last year.
The Queen has experienced “episodic mobility problems” stretching back to last autumn that have led to her cancelling a number of major engagements - including attending part of her Platinum Jubilee celebrations in June.
In October 2021, she used a walking stick at a Westminster Abbey service – the first time she had done so at a major event.
The Queen was admitted to hospital for “preliminary investigations” and had her first overnight stay in hospital for eight years on October 20, 2021.
The next day she was back at her desk at Windsor, carrying out light duties.
Concern for her health mounted when she pulled out of more high-profile engagements, including the Cop26 climate change summit and the Festival of Remembrance, with Buckingham Palace saying she had been advised to continue to rest and to not carry out any official visits.
She was intent on attending the Remembrance Sunday service at the Cenotaph, but missed this due to a sprained back.
For more than three months she carried out only light duties, including virtual and face-to-face audiences in the confines of Windsor Castle.
In February 2022 she celebrated her Platinum Jubilee, meeting charity workers at Sandringham House and cutting a Jubilee cake in what was her largest in-person public engagement since October.
There were fears for her health when she caught Covid in February this year. The triple-vaccinated Queen suffered from mild cold-like symptoms, but said the virus left her “very tired and exhausted”.
She carried on with light duties while self isolating at Windsor, but cancelled some virtual audiences.
She pulled out the Commonwealth Day service at Westminster Abbey in March - a significant date in the royal calendar - and did not attend the Maundy Thursday service.
But she rallied to honour the Duke of Edinburgh at a memorial service at the end of March, walking slowly and carefully with the aid of a stick, and holding on to the Duke of York’s elbow for support.
She thrilled crowds on the first day of her Platinum Jubilee celebrations on June 2 when she appeared on the Buckingham Palace balcony and later at Windsor Castle.
But the next day she pulled out of the Platinum Jubilee Service of Thanksgiving at St Paul’s Cathedral after experiencing “discomfort” during the previous day’s celebrations.
The Braemar Gathering is held on the first Saturday of September, at The Princess Royal and Duke of Fife Memorial Park in the village of Braemar, Aberdeenshire. It is regularly attended by the queen and members of the Royal Family.
It forms part of the Highland games - a series of spring and summer events that have taken place annually in Scotland for centuries, celebrating Scottish and Celtic culture.
The Braemar Gathering sees entrants compete in traditional events such as tossing the caber, tug-of-war, and Highland dancing.