Photos show the Queen at her final royal engagement 2 days before her death

• The Queen's final engagement as head of state was appointing Liz Truss, the UK's new prime minister.
• On Tuesday, the late monarch greeted former Prime Minister Boris Johnson before receiving Truss.

Queen Elizabeth II's final engagement before her death on Thursday was to appoint Liz Truss as the UK's new prime minister.

According to CNN, the late British monarch broke tradition by hosting audiences at Balmoral Castle on Tuesday instead of Buckingham Palace.

A spokesperson for Buckingham Palace told CNN that the Queen, who died aged 96, would not make the trip to London where they're traditionally held. Instead, she received the outgoing leader Boris Johnson, 58, and his partner Carrie Johnson, 34, before appointing his successor Truss, 47, at the Scotland residence.

The meeting with Truss at Balmoral was the Queen's final royal engagement, which took place two days before her death.

A royal source told the publication the 1,000-mile round trip to Balmoral aimed to provide stability in the politicians' diaries, as this would prevent any cancelations caused by the Queen's mobility issues.

After the meeting with Truss, Buckingham Palace announced that the Queen would not be going ahead with an online privy council meeting on Wednesday evening, the BBC reported. The palace added that she had been advised by her doctors to rest after a "full day" on Tuesday and would reschedule.

On Thursday afternoon, Buckingham Palace said that the monarch's doctors were concerned for her health and recommended that she remain under medical supervision. At present, the Queen's cause of death remains unknown but in a statement sent to Insider, Buckingham Palace said she "died peacefully at Balmoral."

Jane Barlow, a Press Association photographer who took the final public pictures of the Queen, told Sky News the monarch "certainly did look more frail" than earlier in the summer but that she was in good spirits. "I got a lot of smiles from her," Barlow added.

Addressing the nation from 10 Downing Street two days into her leadership on Thursday evening, Truss paid tribute to the late Queen in a televised speech. The speech was also shared on the UK Government website.

Truss said: "We are all devastated by the news we have just heard from Balmoral. The death of Her Majesty The Queen is a huge shock to the nation and to the world. Queen Elizabeth II was the rock on which modern Britain was built."

She added that "our country has grown and flourished under her reign" and said "Britain is the great country it is today because of her."

The Conservative party leader also said that the Queen was known for having grace and dignity throughout her 70-year reign, adding that she was loved and admired by citizens of the UK and around the world.

She noted that the crown passed to a new monarch, King Charles, and urged those watching to throw their support behind him.

She concluded her speech by acknowledging Charles as the new king, saying: "We offer him our loyalty and devotion just as his mother devoted so much to so many for so long. And with the passing of the second Elizabethan age, we usher in a new era in the magnificent history of our great country – exactly as Her Majesty would have wished – by saying the words God save the King."