Former footman Paul Whybrew, nicknamed “Tall Paul” within the royal household for his 6ft 4in stature, is part of a team working to decide what will be archived and what will remain confidential.
Mr Whybrew has been trusted by the King to carry out the job, The Mail On Sunday reported, with the newspaper dubbing him the “keeper of the Queen’s secrets”.
It is understood to be too early to decide which documents might eventually be publicly released in the years to come from the Royal Archives.
The Queen kept a handwritten diary, which could offer an unprecedented look at the late monarch’s thoughts and views on political and family life during her long reign.
Her ancestor Queen Victoria charted her thoughts every day in her journals, and the 141 volumes of private diaries have been digitised and released online.
Mr Whybrew, who worked for the Queen for many years, was reported to be so close to the monarch that he would sometimes sit with her watching television.
He featured in the spoof James Bond sequence shown at the London 2012 Olympics, greeting 007 star Daniel Craig at Buckingham Palace and introducing him to the Queen, before accompanying them along a corridor with the corgis.
In 1982, he apprehended the intruder Michael Fagan who had broken into the Queen’s bedroom at the Palace, with the footman congenially distracting him by offering him a drink and serving him a whisky.
Mr Whybrew is working two days a week on the project, using gloves to protect the papers from the Queen’s desk as he sifts through letters and correspondence.
He is part of a team from the Master of the Household’s Department and the Royal Collection Trust.
The late Queen’s wardrobe is among the other items which require cataloguing, but it is understood that Angela Kelly, who was Elizabeth II’s confidante and senior dresser for many years and has since moved out of the Windsor estate, is not currently involved.
Mr Whybrew was made a Commander of the Royal Victorian Order (CVO) for his royal service in Elizabeth II’s demise honours following her death, and he took part in ceremonial processions on the day of her funeral.
Buckingham Palace declined to comment.