The Queen's entire household has reportedly been called to Buckingham Palace in a "highly unusual" move, prompting a frenzy of media activity outside the Royal residence.
Senior royal officer Lord Chamberlain, the Queen's private secretary Sir Christopher Geidt will address aides at 10pm, the Daily Mail reports.
There is intense speculation as to what the meeting is about and a huge media presence has already assembled at the palace.
But rumours of a death or announcement of an abdication were tempered by a source who spoke to Reuters saying: "There's no cause for alarm."
Buckingham Palace did not comment when contacted by HuffPost. It is believed anything newsworthy stemming from the all-staff meeting will be announced later.
Prince Philip was at Lord's cricket ground yesterday and appeared in good health.
Meanwhile the Queen hosted Theresa May at Buckingham Palace.
And according to one Canadian journalist the Palace has confirmed both the Queen and Prince Philip are "alive and well".
HuffPost UK's Head of Video, Dawn Kelly, reported from Buckingham Palace: "There's a quiet sense of anticipation - more cameras are setting up.