What the royal family travelling to Balmoral to see the Queen suggests about her condition
Her Majesty The Queen is currently under medical supervision at Balmoral after doctors became concerned for her health, officials at Buckingham Palace said.
All four of her children are travelling to be by her side at Balmoral Castle, along with her grandson, the Duke of Cambridge.
Prince Charles and Camilla were staying nearby at Birkhall on the Balmoral estate, while Prince William travelled up to Scotland to be with the Queen.
ITV News Royal Editor Chris Ship described the situation as "very serious."
The Duke and Duchess of Sussex, who were scheduled to be doing a charity event in London this evening, are instead travelling to Balmoral Castle.
The Duchess of Cambridge has remained in Windsor, as Prince George, Princess Charlotte and Prince Louis are on their first full day at their new school, Kensington Palace said.
ITV News' Chris Ship understands that Prince William and Kate completed the school run this morning, before being told that he needed to head to Balmoral to see The Queen.
He added: "If you have got the heir to the throne, if you have got the future king Prince William, if you have the Duke of York Prince Andrew heading to Balmoral to see his mother - if you put all of those things together we have a very serious situation.
"Doing what she did on Tuesday, seeing an outgoing and incoming prime minister was clearly a lot for a 96-year-old woman. And, we now have a situation where she is as Buckingham Palace say 'under medical supervision'."
While the scenery changed for this Royal engagement, it was due to The Queen's health.
Buckingham Palace officials had said the move had been to create some 'certainty' in her Majesty's calendar due to on-going mobility issues.
ITV News Royal Editor Chris Ship added: "Balmoral is the place where she goes every summer, and when we say summer it is actually more like August and September and into the first part of October, so there is nothing new about The Queen being at Balmoral - this is where we'd expect to find her.
"The changes of course, very big changes are constitutionally we had a resignation from a prime minister and a leadership election in the Conservative party. And, it is for The Queen to invite her prime minister to form a Government.
"The whole geography had changed from what normally happens at Buckingham Palace to Balmoral castle."
New Prime Minister Liz Truss said: “The whole country will be deeply concerned by the news from Buckingham Palace this lunchtime” adding “my thoughts – and the thoughts of people across our United Kingdom – are with Her Majesty The Queen and her family at this time”.
Labour leader Sir Keir Starmer said he is "deeply worried" by the news from Buckingham Palace and he is hoping for the Queen's recovery.
He tweeted: "Along with the rest of the country, I am deeply worried by the news from Buckingham Palace this afternoon.