The Queen's health has come into focus over the past few months following a stay in hospital, a strained back and now testing positive for coronavirus.
The man in charge of looking after her is Professor Sir Huw Thomas, Head of the Medical Household and Physician to the Queen.
Prof Sir Huw has been Head of the Medical Household since 2014 and was last year knighted after being invested with the Insignia of a Knight Commander of the Royal Victorian Order.
It is likely the Queen wanted to thank Prof Sir Huw personally for his care of her and the royal family.
Prof Sir Huw, who is also professor of gastrointestinal genetics at Imperial College London's department of surgery and cancer, has previously spoken of how grateful he was to be recognised for his service.
Speaking at Imperial at the time of his knighthood, he said: "It's been a busy couple of years in this role, so I feel very grateful to have been recognised for my service to date."
He added: "You very much become part of that organisation and become the personal doctor to the principal people in it, who are patients just like other patients.
"With the pandemic, the key priority of the Medical Household is trying to make sure that the people under its care are kept safe."
It is likely to have been Prof Sir Huw who advised the head of state to take things easy after she underwent preliminary tests in King Edward VII's Hospital on October 20, 2021.
The Queen subsequently suffered a back problem causing her to miss the 2021 Remembrance Sunday service.
Despite testing positive and experiencing "mild cold-like symptoms", Buckingham Palace said the Queen expects to continue carrying out "light duties".
The Queen has received coronavirus vaccinations and was cared for at Windsor in "HMS Bubble" - the nickname for their reduced household of loyal staff - during lockdown alongside her late husband the Duke of Edinburgh before his death in April 2021.
Professor Sir Huw has also been involved in delivering some of the younger members of the Royal Family.
He was part of the team who looked after the Duchess of Cambridge when she gave birth to daughter Charlotte in 2015 and youngest son Louis in 2018 at St Mary's Hospital, Paddington, alongside Guy Thorpe-Beeston, surgeon gynaecologist to the royal household, and consultant gynaecologist Alan Farthing, surgeon gynaecologist to the Queen.
Mr Farthing works as a consultant at St Mary's Hospital and Queen Charlotte's Hospital in Shepherd's Bush and replaced Sir Marcus Setchell in the role when the latter retired in 2013.
Mr Farthing was also engaged to Jill Dando at the time of her murder in April 1999 and helped found the Jill Dando Institute of Security and Crime Science at University College London following her death.
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