Speculation amongst Buckingham Palace staff is reportedly rampant after the Queen's most senior aides called her entire household to an emergency meeting later today.
Servants from royal residences across the country have been ordered to London and will be addressed this evening (NZ time) by the Lord Chamberlain, the most senior officer of the Royal Household, as well as Her Majesty's right-hand man, Private Secretary Sir Christopher Geidt, the Daily Mail says.
Even her longest-serving staff were left in the dark about why the meeting was being called but multiple sources said it was "highly unusual" and had sparked fevered talk about an imminent announcement concerning the monarch or her husband, the Duke of Edinburgh, according to the Daily Mail report.
"Everyone is on tenterhooks," said one.
"Although meetings involving the entire royal household are occasionally called, the way this has been done at the eleventh hour is highly unusual and suggests that there is something major to be disseminated.
"But at the moment, only those closest to her genuinely know what on earth this is all about."
Staff from royal residences such as Windsor Castle and Sandringham have been asked to come in, as well as those from further afield as Balmoral in Scotland, suggesting that that any announcement will affect them all.
Buckingham Palace declined to comment.
Sources insisted that the Lord Chamberlain does call meetings of household staff from time to time and said it would be wrong to speculate further.
The Queen has just returned to her London residence following her extended Easter break at Windsor.
She turned 91 last month while her husband, Prince Philip, will celebrate his 96th birthday in June.
In recent years the Queen has, slowly but surely, been handing over a number of her more onerous duties including all those involving long-haul travel and many of her regular investitures.
Last year Buckingham Palace also announced that she would step down as patron of around 25 national organisations, including the NSPCC and Wimbledon tennis, after she turned 90 in April and in favour of younger members of her family.
Many have expressed concern, however, that she still conducts well more than 300 engagements every year.
Recently the Duke and Duchess of Cambridge announced they would be finally moving back to London from Norfolk, where Prince William works as an air ambulance pilot, in order to help shoulder the burden more.
Similarly, Prince Philip has been curtailing his commitments, having stepped down from a number of patronages when he turned 90.
There was also grave concern for the Queen and Philip's health over Christmas when both developed heavy colds, forcing the monarch to miss Christmas Day service for the first time in living memory.
It is unlikely, however, that any meeting would involve news of an abdication as the Queen has always vowed to serve her country for as long as she lives.