Updated: Sep 10, 2022
The Queen is under medical supervision at Balmoral after doctors became concerned for her health, Buckingham Palace has said.
Prince Charles has travelled to Balmoral.
The Duchess of Cornwall has also travelled there and the Duke of Cambridge is on his way.
The Duke of York - Prince Andrew - is on his way to Balmoral. The Count and Countess of Wessex, Edward and Sophie, are also travelling there, and Princess Anne is already in Scotland where she had been undertaking engagements.
All the Queen's children are either at or travelling to Balmoral says BBC Royal Correspondent Jonny Dymond.
"Following further evaluation this morning, the Queen's doctors are concerned for Her Majesty's health and have recommended she remain under medical supervision," a statement said.
"The Queen remains comfortable and at Balmoral."
The announcement comes after the Queen, 96, pulled out of a virtual Privy Council on Wednesday, with doctors advising her to rest.
Jonny Dymond, BBC Royal Correspondant, said on BBC Radio 4: "There is a degree of seriousness that we have not seen before, the very fact that the statement was issued when the palace is so reticent about making any commentary on the Queen's health.
"The phrasing of the statement, that the Queen’s doctors are concerned about her health and she remains under medical supervision, and the movement of the most serious members of the Royal Family towards Balmoral, towards the Queen, all of those indicate a clear degree of concern for the health of the 96-year-old Queen.
"We're not going to get great clarity from the palace, because they do not reveal the details of the health of senior members of the Royal Family.
"But the fact that the family is gathering at Balmoral is an indication of the seriousness of the situation."
Prime Minister Liz Truss said the "whole country" would be "deeply concerned" by the news.
"My thoughts - and the thoughts of people across our United Kingdom - are with Her Majesty The Queen and her family at this time," she added.
The Queen appointed Ms Truss as prime minister at Balmoral on Tuesday, instead of travelling to London for the event.
During her 70-year reign the Queen has typically had an audience with her new prime minister at Buckingham Palace.
She has been on a summer break at her Scottish home since July. For live updates visit: https://www.bbc.co.uk/news/live/uk-62834633