Friday marks D-Day +7, or D+7, in the plans marking the Queen’s death.
Here is the timeline of events expected to take place over the next 24 hours.
The couple will then go to the Welsh Parliament where they will receive condolences and meet members of the Senedd.
From there they will travel to Cardiff Castle where Charles will hold a private audience with Welsh First Minister Mark Drakeford and the presiding officer, before attending a reception hosted by the Welsh Government.
A protest against the monarchy is expected to take place outside the castle.
On his return to Buckingham Palace, the King will host faith leaders in the Bow Room.
The Prince and Princess of Wales will visit Army Training Centre Pirbright in Surrey to meet troops from the Commonwealth who have been deployed to the UK to take part in the state funeral of Her Majesty The Queen.
Lying in state:
The lying in state continues. From 7.30pm, the Vigil of the Princes takes place at Westminster Hall, carried out by Queen’s four children (The King, Princess Royal, Duke of York and Earl of Wessex).