Sky News understands the decision was made for the comfort of Her Majesty, who has been suffering from mobility problems since last year. The Prince of Wales will join spectators on Saturday for the rally, which draws crowds from around the world to watch competitors take part in the shot put, hammer throw and tug of war. It comes as the Queen announced she will appoint the new Prime Minister at Balmoral for the first time in her reign – in what has been described as a “huge break with tradition”. The monarch will receive either Liz Truss or Rishi Sunak on Tuesday, September 6 – a day after one of them was announced as Boris Johnson’s replacement and handed over the keys to 10 Downing Street. New prime ministers are usually appointed from Buckingham Palace or Windsor Castle. Whoever wins the Conservative leadership race will officially become the 15th British prime minister appointed by the Queen, who first confirmed Winston Churchill to power in 1951. Her Majesty celebrated her Platinum Jubilee this year but pulled out of a series of events to mark her historic 70 years on the throne. Use Chrome browser for more accessible video player 1:19 Instead of Buckingham Palace, the new Prime Minister will travel to Balmoral to be officially appointed by the Queen The guest of honor “reluctantly” abandoned plans to attend a thanksgiving service at St Paul’s Cathedral after feeling unwell during the first day of Jubilee events, including a birthday parade and flypast. Concerns have grown over the health of the Queen, who is often pictured either sitting or using a cane. Earlier in May, the Queen missed the opening of Parliament for the first time in 59 years on doctors’ orders after experiencing “episodic mobility problems”. Charles, 73, stepped in to read Her Majesty’s speech as he and the Duke of Cambridge jointly opened the new session of Parliament on behalf of the Queen, as Councilors of State. The monarch was also forced to miss Royal Ascot for the first time since her coronation in June. And he pulled out of the traditional Easter Sunday service at St George’s Chapel in Windsor this year. Instead, his grandson Prince William and his wife Kate led the royals at the annual royal event.