Queen Elizabeth II was instructed to rest after doctors declared that she needed to do so after a "full day yesterday," when she met with newly appointed Prime Minister Liz Truss.
The Queen had to cancel her Privy Council advisory group meeting, but it will be postponed until she is ready.
In a statement, Buckingham Palace said, "After a full day yesterday, Her Majesty has this afternoon accepted doctors' advice to rest."
The 96-year-old monarch met with Truss on Tuesday at Balmoral in the Scottish Highlands, the Queen's traditional summer retreat.
The tradition between the royal family and heads of state in England is rooted in centuries of tradition. But also, Prime Ministers, going back to 1952 and Winston Churchill, have greeted Queen Elizabeth II for approvals in Buckingham Palace in London. Truss made history this year as the first Prime Minister to meet with Queen Elizabeth outside of London.
As AFP reported, the Queen has been dealing with some health ailments, including walking certain distances and standing for certain amounts of time since at least 2021, causing several public engagements to need to be canceled or postponed. Royal officials have described her condition as "episodic mobility problems."
The Queen recovered from a period with COVID-19 earlier this year that "exhausted" her, royal officials said.