It has also prompted speculation over what the monarchy will look like when her son, Prince Charles, 72, ascends to the throne. Her Majesty, 95, was spotted on Monday driving alone around the grounds of Windsor Castle in sunglasses and a headscarf. On Friday, Buckingham Palace confirmed Her Majesty would not attend COP26 alongside other senior royals, including the Prince of Wales.
The Queen had been advised to rest for a further two weeks and avoid royal visits during that period. She is still able host virtual audiences and complete light duties.
Her Majesty will address delegates and media at COP26 via a pre-recorded video message.
The Palace also detailed the Queen’s “firm intention” to attend the Remembrance Sunday service on November 14 at the Cenotaph.
In an opinion piece for Bloomberg, Martin Ivers addresses the Queen's decision not to attend COP26.
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Mr Ivers writes: "This is but the latest of several intimations of royal mortality.
"The Queen, 95 years old this year, long ago handed over arduous foreign tours to her son and heir to the throne, Prince Charles.
"Just as the Palace begins to transfer more duties around the royal 'firm', the U.K. must begin to think the unthinkable: of life without her."
In a statement, Buckingham Palace said: "The doctors have advised that Her Majesty can continue to undertake light, desk-based duties during this time, including some virtual audiences, but not to undertake any official visits.
"Her Majesty regrets that this means she will be unable to attend the Festival of Remembrance on Saturday, November 13."
This follows the cancellation of Her Majesty’s trip to Northern Ireland in October, after the Queen "reluctantly accepted medical advice to rest for the next few days".
Her Majesty also spent a night at King Edward VII’s Hospital in central London for “some preliminary investigations,” but returned to her home at Windsor the next day “in good spirits.”
The hospital visit was Her Majesty’s first in eight years.
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Prime Minister Boris Johnson, soon after Her Majesty arrived back at Windsor Castle, said he was "given to understand that, actually, Her Majesty is characteristically back at her desk at Windsor as we speak".
However, prominent senior royals have been seen taking on further royal duties as signs of Her Majesty’s advancing age become more obvious.
Royal commentators note Her Majesty’s hectic schedule since the the start of October.
The monarch has met virtually with a number of high-profile politicians since she resumed royal duties last month, including speaking with the Japanese ambassador Hajime Hayashi and the EU ambassador Joao de Almeida.
The previous day, Her Majesty chatted with the new governor-general of New Zealand, Dame Cindy Kiro.
She also enjoyed a day at Ascot, spotted at Champions Day in mid-October.
Prior to the scheduled trip to Northern Ireland, the Queen also hosted the Global Investment Summit, throwing open the doors of Windsor Castle to the likes of Bill Gates, US climate envoy John Kerry and Boris Johnson.
She was accompanied by the Prince of Wales and her grandson, the Duke of Cambridge, as royal experts note the increased the presence of senior royals at the Queen’s official engagements.
In a recent visit to Cardiff last month, the Queen was flanked by the Prince of Wales and Camilla, Duchess of Cornwall, as she opened the Welsh Parliament.
At the event, she was photographed using a walking stick for the second time, following her attendance at Westminster Abbey for an event celebrating the Royal British Legion.
At the centenary celebration, the Queen was spotted using her walking stick for the first time in 20 years, as she was accompanied by her daughter, Anne, Princess Royal.
It was the first time that Her Majesty had used a stick for comfort, rather than for specific medical reasons.
It was also noted that the Queen used an entrance thought to be a shorter distance to her seat inside the Abbey than the conventional, main entrance to the building.
These signs of the age of the longest-reigning monarch have continued to fuel worries over the Queen’s health, with Her Majesty celebrating her Platinum Jubilee in 2022.