The prime minister has joined the King and Queen at a church service close to Balmoral Castle.
Rishi Sunak was following decades of tradition by spending the weekend at the monarch's Scottish estate.
The King is continuing a precedent set by his mother, Elizabeth II, who had 14 of her 15 prime ministers to stay.
On Friday, it will be a year since the Queen's death and her eldest son's accession.
A day before the return of parliament following the summer break, Mr Sunak was driven to Crathie Kirk separately from the King and Queen.
The King wore a kilt while the Queen was in a green coat and hat and carrying a beige handbag.
They were joined at the 19th century parish church, which overlooks the River Dee, by Princess Anne and her husband, Vice Admiral Sir Tim Laurence.
Former prime minister David Cameron once said there was not much "chillaxing" at Balmoral because the royals like to spend their time on outdoor pursuits.
Previous guests have also remembered family barbecues, during which Prince Philip, the late Duke of Edinburgh, did the cooking and the late Queen did the washing up.
On Saturday, tributes were paid to Queen Elizabeth II as the King and Queen enjoyed events at the Braemar Gathering.
The highland games event, which takes place just a short drive from Balmoral Castle, was always a firm favourite of hers.