Today marks the one year anniversary of Queen Elizabeth II's deathPA
The King said in a statement: "In marking the first anniversary of Her late Majesty's death and my Accession, we recall with great affection her long life, devoted service and all she meant to so many of us.
"I am deeply grateful, too, for the love and support that has been shown to my wife and myself during this year as we do our utmost to be of service to you all. Charles R."
The King and Queen were accompanied by a small number of guests but the Prince and Princess of Wales were not among them.
William and Kate are visiting Wales today as part of their tribute to the late Queen.
The pair also released a statement honouring Queen Elizabeth: “Today we remember the extraordinary life and legacy of Her Late Majesty Queen Elizabeth.
"We all miss you. W & C"
They will visit St Davids Cathedral to attend a private service honouring the late monarch.
Elsewhere, Prince Harry has made a surprise appearance to St George’s Chapel.
The church is where both Queen Elizabeth II and Prince Philip are buried.