Queen Elizabeth II died on Thursday after an unprecedented 70-year reign as the UK's monarch.
Her son, King Charles III, is now the oldest person in British history to become king at age 73.
"We mourn profoundly the passing of a cherished Sovereign and a much-loved mother," he said.
With Queen Elizabeth II's death on Thursday, King Charles III has now become the oldest person in British history to be king — at age 73.
"Today the crown passes, as it has done for more than 1,000 years, to our new monarch — our new head of state — His Majesty King Charles III," UK Prime Minister Liz Truss said as she addressed the nation.
"With the king's family, we mourn the loss of his mother, and as we mourn, we must come together as a people to support him," Truss said. "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.'"
In the first statement released by King Charles III as King, he called Queen Elizabeth's death "a moment of the greatest sadness for me and all members of my family."
"We mourn profoundly the passing of a cherished Sovereign and a much-loved mother," he continued.
The last time that the United Kingdom saw a change in leadership was 70 years ago when the Queen took over after King George's death. The previous oldest king in British history dates back to 1830 when King William IV ascended the throne at 64 years old.
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