Prince Edward and Sophie Arrive in Scotland Amid Queen's Health Concerns

 Prince William, Prince Andrew, Prince Edward and Sophie Arrive in Scotland Amid Queen's Health Concerns

The royal family members flew north to see Queen Elizabeth at Balmoral Castle in the Scottish Highlands, where she is under medical supervision.

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After landing, the four royals must drive an hour west to be with Queen Elizabeth at her summer retreat in the Scottish Highlands, where she's been since July. They will join Prince Charles and his wife, Camilla, Duchess of Cornwall. The 73-year-old heir to the throne was in Scotland Wednesday carrying out engagements.

Princess Anne, the Queen's only daughter, was also already in the country for royal duties, and is making her way to Balmoral to be the monarch's side. Also en route is Prince Harry, who flew to Europe this week with wife Meghan Markle for a for a series of visits with their longstanding charitable causes.

The Queen was last seen in photos on Tuesday, where she appointed Conservative Party leader Liz Truss as the new prime minister of the United Kingdom at Balmoral — a historic first. The monarch has been experiencing episodic mobility issues, and a source tells PEOPLE that the decision was made to host the audience as Balmoral to provide certainty for schedules.

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Responding to the palace's statement on the news of the Queen's health Thursday, Truss shared words of support.

"The whole country will be deeply concerned by the news from Buckingham Palace this lunchtime. My thoughts - and the thoughts of people across our United Kingdom - are with Her Majesty The Queen and her family at this time," the new premier tweeted.My youtube channel