The Queen’s family rushed to be with her at Balmoral this afternoon.
Buckingham Palace issued a statement at 12.32pm on Thursday saying royal doctors were concerned for her health.
They said the head of state was comfortable and royal physicians have recommended she stays under medical supervision.
Her son, the Prince of Wales, and second in line to the throne, Prince William, cleared their diaries to dash to the Queen’s Scottish Highlands home.
The Queen’s four children – Charles, the Princess Royal, the Duke of York and the Earl of Wessex – also went to her side, joined by the Duchess of Cornwall and the Countess of Wessex.
An RAF plane that landed in Aberdeen just before 4pm was carrying the Duke of Cambridge, Andrew, Edward and Sophie.
The Duke of Sussex travelled alone without the Duchess of Sussex, who had been planning to accompany him to Scotland.
The Duchess of Cambridge remains in Windsor to take care of her and William’s children, who had their first full day at their new school on Thursday.
The Queen, 96, pulled out of a virtual Privy Council on Wednesday, a day after appointing Liz Truss as Prime Minister at Balmoral.
Messages of concern
Messages expressing deep concern flooded in from political leaders, while the Archbishop of Canterbury said the “prayers of the nation” are with the Queen.
The Queen has had ongoing mobility issues and looked bright but frail while using a walking stick during Tuesday’s audience with Ms Truss, which followed a visit from outgoing prime minister Boris Johnson as he tendered his resignation.
Speaker Sir Lindsay Hoyle interrupted a speech by SNP Westminster leader Ian Blackford, during an energy debate in the House of Commons, to tell MPs: “I know I speak on behalf of the entire House when I say that we send our best wishes to Her Majesty the Queen and that she and the royal family are in our thoughts and prayers at this moment.”
He added: “If there is anything else, we will update the House accordingly.”
Ms Truss was on the front bench of the Commons after her first major policy intervention as PM when she received the news about the Queen’s health.
The initial indication that something was wrong came as Chancellor of the Duchy of Lancaster, Nadhim Zahawi, came into the Chamber, sat down next to Ms Truss and began urgently speaking to her while she was listening to Labour leader Sir Keir Starmer’s response to her energy statement.
Sir Keir, too, was passed a note by his deputy Angela Rayner, with Commons Speaker Sir Lindsay Hoyle also handed a piece of paper updating him about the developing situation.
The Queen missed the annual Braemar Gathering highland games, which she usually attends, last weekend.
During her Platinum Jubilee celebrations, the Queen only travelled to Buckingham Palace twice, first for her Trooping the Colour balcony appearance and then for a finale after the pageant.
She secretly spent a night in hospital for tests in October and was ordered by doctors to rest for the next three months, missing the Remembrance Sunday Cenotaph service and Cop26 climate change talks.
The Queen caught Covid in February.
After experiencing mild cold-like symptoms, she said the virus left her “very tired and exhausted”.