In the House of Commons, Speaker Sir Lindsay Hoyle relayed the news.
“I wish to say something about the announcement which has just been made about Her Majesty,” he said.
“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.”
The BBC reported notes had been passed to various members including Prime Minister Liz Truss and Labor leader Keir Starmer before the palace’s announcement was made public.
Hoyle promised to update the gathered politicians if there was more news.
Royal watchers noted the seriousness of the palace’s statement from an institution prone to “understatement” regarding the 96-year-old’s health.
Members of the royal family were travelling on Thursday to be by the monarch’s side in Scotland’s Balmoral Castle, where the Queen was said to be “comfortable”.
Truss, who the Queen appointed to her position earlier in the week, 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 said, in a tweet.
Starmer expressed similar wishes, as did Scottish First Minister Nicola Sturgeon and former prime ministers David Cameron and Tony Blair.
“Along with the rest of the country, I am deeply worried by the news from Buckingham Palace this afternoon,” Starmer said.
