There are mechanisms that would kick into gear in the event that The Queen cannot undertake her official duties as Sovereign on a temporary basis due to illness or absence abroad.
If that were to happen, two or more Counsellors of State are appointed by Letters Patent to act in Her Majesty's place.
However, the protocol would place Prince Harry and Prince Andrew in an unprecedented position.
If Her Majesty were temporarily incapacitated, both Harry and Andrew still have the right to become a Counsellor of State.
According to the Cabinet Manual, published in October 2011: “When the sovereign is absent from the country for a short period or temporarily incapacitated or for some definite cause not available, his or her functions are delegated to Counsellors of State.
“These are currently the sovereign’s spouse and the four nearest in line to the throne.
“Two or more Counsellors of State may exercise any of the functions of the sovereign except the powers to grant any rank, title or dignity of the peerage, or to signify royal assent to any amendment to the Act of Settlement 1700 or royal style and titles.”
While under the rules, the five Counsellors of State currently would include Prince Philip, Prince Charles and Prince William, if they were incapacitated, other royals would be called upon.
Her Majesty does have the right to make decisions about who she wants to be a Counsellor of State, as she requested in 1952 that the Queen Mother be added to the list of Counsellors.
However, as Harry and Andrew currently retain all their rights in the line of succession, it would be highly unusual for the Queen to bar them from any duties linked to those rights.
According to The Royal Family’s website: “Counsellors of State are appointed from among the following: The Duke of Edinburgh and the four adults next in succession (provided they have reached the age of 21).
The current Counsellors of State are These are currently The Prince of Wales, The Duke of Cambridge, Prince Harry and The Duke of York.”