The Queen is resting at Windsor Castle after she was forced to pull out of attending the Remembrance Sunday service at the Cenotaph due to a back sprain.
This was only the sixth time the Queen has missed Remembrance Service during her 69-year reign.
Previous reasons given for her not attending were pregnancy, which meant she did not attend on two occasions, and four other times when she was abroad on tour.
Last month the 95-year-old monarch had her first overnight stay in hospital eight years "following medical advice to rest".
Courtiers are now understood to now be taking a “cautious approach” with the Queen’s diary with no public engagements expected for the rest of the year.
According to a source, senior royals have vowed to step in and help with the Queen’s diary “for as long as is needed".
With plans already underway for the four-day celebrations to mark the Queen Platinum Jubilee, one royal expert said they are now being reassessed.
Jennie Bond told the BBC: "Everyone at the palace now will be very carefully calculating, probably recalculating exactly what can be done for the Platinum Jubilee.
"The priority has got to be obviously the Queen's health and the Queen's safety.
"I think what we're seeing now is a gradual transition of responsibility from the Queen to Prince Charles, Prince William, and other senior members of the royal family."
She added that she believes while Charles and William will front the celebrations "the Queen will pop up here and there for the big days themselves".
The celebrations will be staged at the official royal residences, including Buckingham Palace, Windsor Castle and the Palace of Holyroodhouse.
As the event is still seven months away the Queen has plenty of time to make a recovery and could return to her appointments in the New Year.
Joe Little, managing editor of Majesty magazine, said: "The Platinum Jubilee programme will reflect her age, although the Palace won't say as much, and other people will be doing engagements on her behalf.
"We know she won't go to the Commonwealth or do any tours, but how much she does in the UK will be interesting to see."
The extended bank holiday, from Thursday 2nd to Sunday 5th June, will begin with Trooping the Colour, which will be staged in full for the first time since the pandemic.
This will be followed by a service of thanksgiving for the Queen's 70-year reign at St Paul's Cathedral on the Friday.
It has an eye-popping budget of between £10million and £15 million.
