The Prince of Wales is scheduled to attend the funeral on September 9 on his father’s behalf, having similarly represented the King at Pope Francis’s funeral last year.

British monarchs do not attend funerals of other heads of state per protocol, usually sending another member of the royal family to represent them.

Charles, 77, who is being treated for an undisclosed form of cancer but maintains a packed schedule of engagements, released a statement mourning the loss of his "dear cousin" King Harald last week.

The two men were second cousins once removed, both being descendants of Britain's King Edward VII.

Charles's sister Princess Anne will attend in a personal capacity as the godmother of the new king, Haakon VIII.