King Charles III to address nation as UK mourns Queen Elizabeth's demise

Britain's King Charles III will address a nation in mourning following the death of his mother Queen Elizabeth II, the only monarch most Britons ever knew.

Charles, who raced to be by the side of the queen at her Scottish home on Thursday, was due to travel back to London with his wife Camilla, now Queen Consort, before meeting  Prime Minister Liz Truss and making a televised statement.

Waking up to their first day without a woman once described by her grandson Harry as "the nation's grandmother", members of the public began gathering again outside Buckingham Palace to lay flowers and take photos of the growing memorial there.

At the remote Balmoral Castle in Scotland where she died on Thursday and where her family are gathered, people also arrived to pay their respects.

READ MORE: Queen Elizabeth II, Britain's longest-serving monarch, dies at 96

Moment of great sadness

Charles, who automatically succeeded his mother, Queen Elizabeth, said her death was a moment of great sadness for himself and his family.

"We mourn profoundly the passing of a cherished Sovereign and a much-loved mother. I know her loss will be deeply felt throughout the country, the Realms and the Commonwealth, and by countless people around the world," the 73-year-old said in a statement.

Regular business in parliament was scrapped and replaced with a special session for lawmakers to pay tribute to the queen, due to start at 1100 GMT.

Parliament will also convene on Saturday, something it rarely does, and will approve a formal message of condolence to the king.

READ MORE: 'End of an era': Reaction from world leaders to Queen Elizabeth's death