The Queen is said to be surrounded by loyal aides as she rests for two weeks on doctors' orders.
Dresser Angela Kelly and courtier Paul Whybrew are said to be a source of support for the Queen amid mounting concerns for her health.
Her Majesty has been forced to scrap public engagements for the next fortnight and carry out only "light, desk-based duties".
The 95-year-old spent one night in hospital earlier this month and has been seen using a walking stick in recent weeks.
It was announced last Wednesday the Queen had "reluctantly" accepted medical advice to rest and cancelled her trip to Northern Ireland that was scheduled to begin that day.
But it later emerged she had stayed overnight in King Edwards VII's Hospital in central London.
Buckingham Palace confirmed the head of state had undergone "preliminary investigations" during her first overnight stay at a medical facility in eight years.
Now, she is resting up at Windsor Castle with the support of trusted aides who previously cared for the monarch and Prince Philip in the so-called 'HMS Bubble' during the first Covid lockdown.
Mr Whybrew, said to be the Queen's favourite courtier and known as 'Tall Paul' due to his 6ft 4in frame, and Ms Kelly are said to be a "near constant presence" by the monarch's side, reports the Mail on Sunday.
The Queen and her dresser are known to be close, with Her Majesty even granting her rare permission to write a book on her career inside the Palace.
Mr Whybrew, who is officially Page of the Backstairs, came to public attention in 2012 during the opening ceremony James Bond sketch for the London 2012 Olympic Games.
The courtier has reportedly been watching television with the Queen, while Ms Kelly also helps to keep her company.
A Palace source told the newspaper: "The Queen is very grateful for the loyal support she has received."
The Queen and her late husband, the Duke of Edinburgh, were attended to by a reduced household of around 20 staff in what was dubbed HMS Bubble last year as the country went into lockdown.
Following Prince Philip's death in April this year, her closest aides have been a source of support.
Among those closest to her are head groom, Terry Pendry and private secretary Sir Edward Young.
The group, including Ms Kelly and Mr Whybrew, was christened 'HMS Bubble', a joke the Queen and Prince Philip were said to find very amusing, by Vice-Admiral Sir Tony Johnstone-Burt, master of the household.
It comes as the Queen will reportedly worship at home today and is expected to be given a private Holy Communion after doctors told her to rest.
Several of the monarch's royal engagements have been cancelled, including the COP26 climate change conference which starts in Glasgow today.
On Saturday, Prime Minister Boris Johnson insisted the Queen is on “very good form” and it's understood he spoke to the monarch as part of his normal weekly audience.
The Queen underwent tests in hospital last week and cancelled a two-day trip to Northern Ireland.
In a statement Buckingham Palace announced: "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."
It was announced last Wednesday the Queen had "reluctantly" accepted medical advice to rest and cancelled her trip to Northern Ireland that was scheduled to begin that day.
But it later emerged she had stayed overnight in King Edwards VII's Hospital in central London.
Buckingham Palace confirmed the head of state had undergone "preliminary investigations" during her first overnight stay at a medical facility in eight years.
