Queen Elizabeth II’s final royal engagement was Tuesday, Sept. 6, at Balmoral Castle in Scotland. She appointed new Prime Minister Liz Truss just a few days before her passing. 

On her 21st birthday in 1947, then-Princess Elizabeth went on the radio and made a promise to Britain and its commonwealth nations. 

At the time, she pledged that "my whole life, whether it be short or long, will be devoted to your service." The long-reigning monarch has fulfilled that vow over the years, including with Tuesday's engagement. 

In the past, the meeting between the incoming prime minister and the queen has always taken place at Buckingham Palace in London. However, the location was changed due to the queen’s mobility issues and her potential inability to travel back to London, making this the first time in 70 years this ceremonial tradition took place outside of Buckingham Palace.

QUEEN ELIZABETH II, LONGEST-REIGNING BRITISH MONARCH, DEAD AT 96

At the meeting, the monarch traditionally asks the new prime minister to form a government to be sworn in later. Truss and her newly appointed cabinet members were scheduled to be sworn in at the Privy Council meeting Wednesday, but it was postponed after the queen was advised by doctors to rest.

"After a full day yesterday, Her Majesty has this afternoon accepted doctors’ advice to rest," the palace said in a statement. "This means that the Privy Council meeting that had been due to take place this evening will be rearranged."

The queen had been experiencing episodes of mobility issues and had been walking with a cane since October 2021. In November 2021, the monarch decided against attending a Remembrance Day ceremony because she had a sprained back.

The queen had been taking a step back from many of her royal duties and instead giving her son, now King Charles, more responsibilities. Her grandson, Prince William, has also taken on more responsibility and made appearances as a senior royal.

On Thursday, the queen died at Balmoral Castle at the age of 96. She was remembered by many, including Truss, for her unwavering dedication to her country and the crown.

"Queen Elizabeth II was the rock on which modern Britain was built. Our country has grown and flourished under her reign. Britain is the great country it is today because of her," Truss said during a speech on BBC News. 

"Earlier this week, at 96, she remained determined to carry out her duties as she appointed me as her 15th prime minister."

Queen Elizabeth began her reign in 1952 at just 25 years old when her father, King George VI, died in his sleep. Earlier this year, the queen celebrated her 70-year reign with a Platinum Jubilee. 

Following the news of her passing, world leaders across the globe spoke out, expressing their condolences to the royal family and paying tribute to the late monarch. President Biden and first lady Jill Biden called her the "first British monarch to whom people all around the world could feel a personal and immediate connection." Scottish First Minister Nicola Sturgeon called her life "one of extraordinary dedication and service."

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Hollywood has also flooded social media with condolences, remarking on her dedication to service.

Elton John wrote the queen "led the country through some of our greatest and darkest moments with grace, decency and a genuine caring warmth." 

J.K. Rowling said, "She did her duty by the country right up until her dying hours, and became an enduring, positive symbol of Britain all over the world. She’s earned her rest."

"It feels as though we lost a friend: a dedicated Monarch who inspired all of us with her love, wisdom and grace," Dame Julie Andrews said in a statement. "May we honour her by holding to the standards she set for herself and her nation."

The queen officially became England's longest-reigning British monarch in 2015 when she exceeded her great-great-grandmother Queen Victoria’s reign. Queen Elizabeth held the throne 70 years and holds the record for second-longest reigning monarch in the world, second only to French King Louis XIV, who ruled for 72 years.

The Associated Press contributed to this report