Charles III paid tribute to Queen Elizabeth as he was formally announced as the nation's new king.
Charles made the personal declaration during the Accession Council meeting where he was declared the new monarch. A proclamation will follow on the balcony later in the morning.
Paying tribute to the Queen at the Accession Council, the King said: “Her reign was unequalled in its duration, its dedication and its devotion. Even as we grieve, we give thanks for this most faithful life.”
Read more: King Charles tells how Queen's death was 'the day I have been dreading'
In a personal declaration to his late mother, King Charles added: "I know how deeply you and the entire nation, and I think I may say the whole world, sympathise with me in this irreparable loss we have all suffered.”
Broadcast cameras were allowed into the historic event giving the world a first glimpse of an ancient ceremony dating back centuries – and one of the first changes to convention instigated by the new King.
More than 200 privy councillors – a group of mostly senior politicians past and present, some members of the monarchy and other national figures – were present to hear the Clerk of the Council read the Accession Proclamation.
Charles became king as soon as his mother died. But the Accession Council meeting is part of the formal process for announcing the start of a new reign. A coronation will follow, but months later.
The new King Charles also declared a bank holiday for the day of Queen Elizabeth II's funeral.
Read next: