What happens if King Charles can no longer perform his duties?

King Charles III’s cancer diagnosis will turn minds to the question of what happens if he becomes unable to fulfil his constitutional duties. Buckingham Palace has announced he will continue performing his official paperwork and his weekly meetings with the prime minister throughout his treatment.But what happens if he becomes seriously ill?

There are three options: counsellors of state, regency and abdication.

Counsellors of state

First, King Charles can delegate some or most of his royal functions to counsellors of state, as happens most commonly when he is travelling overseas. Two counsellors of state act jointly in exercising royal powers such as assenting to laws, receiving ambassadors and holding Privy Council meetings.

The counsellors of state are the spouse of the sovereign and the next four adults in line of succession to the throne – being Queen Camilla, Prince William, Prince Harry, Prince Andrew and Princess Beatrice.

However, Prince Harry is excluded while he is outside the United Kingdom, and in practice Prince Andrew and Princess Beatrice are not called on to act as they are not “working royals”.

As this left only Queen Camilla and Prince William to perform the role, a law was passed in the UK in 2022 to add Princess Anne and Prince Edward to the list.

Counsellors of state may carry out most of the sovereign’s functions while he is ill, but they cannot dissolve parliament, except on his instruction, and they cannot create peers. Whether they can appoint a prime minister remains a matter of debate. Most significantly, they cannot exercise powers with respect to the King’s other realms, such as Australia.

Regency

The second option is a regency. This occurs if the King “is by reason of infirmity of mind or body incapable for the time being of performing the royal functions”. The sovereign does not control when or for how long a regency occurs. Instead, it is initiated by a declaration of three or more of: the sovereign’s spouse, the lord chancellor, the speaker of the House of Commons, the lord chief justice of England and the master of the rolls.

The UK’s Regency Act requires Prince William to be regent, as he is the next adult in line of succession to the crown. The regent has the powers of the King with respect to the United Kingdom, but cannot change the order of succession to the crown.

The Regency Act does not give the regent powers in relation to realms such as Australia and New Zealand. New Zealand resolved the problem by inserting a section into its Constitution Act which provides that whoever is made regent under the law of the UK may perform the royal functions of the sovereign with respect to New Zealand. Australia, however, has done nothing in this regard, so a British regent would have no powers with respect to Australia.

Read more: What are the legal and constitutional consequences for Australia of Queen Elizabeth II's death?

Abdication

The final option for an incapacitated monarch is abdication. This leads to difficult questions about how an abdication would operate in relation to each of the realms.

When King Edward VIII abdicated in 1936, it was achieved by both a signed instrument of abdication and the enactment of legislation to which the various realms, including Australia, assented. This is not possible today, as the UK can no longer legislate with respect to Australia.

Abdication would therefore raise difficult questions about whether there needed to be a separate abdication of the King of Australia, to trigger the application of the rules of succession that are now part of Australian law, or whether covering clause 2 of the Constitution, which defines the sovereign by reference to Queen Victoria’s “heirs and successors in the sovereignty of the United Kingdom”, would apply.

Because of the potential constitutional messiness of dealing with the King’s role in his 14 realms beyond the United Kingdom, it is likely abdication would be avoided.

Consequences for Australia

If King Charles were incapacitated and counsellors of state or a regent were appointed, would this cause any real problem in Australia?

The King’s only remaining substantial powers with respect to Australia are the appointment and removal of the governor-general and the state governors. The governor-general’s term is expected to expire in the middle of the year. If King Charles were then seriously ill and unable to appoint a new governor-general, no one could do so, as neither counsellors of state nor a regent could do so.

Instead, the current governor-general, David Hurley, could choose to continue in office, as there is no formal termination of his office until he is replaced.

Alternatively, he could resign and his office could be filled on a temporary basis by a state governor as administrator, as is the usual practice when there is a vacancy in the office. If the office of a state governor becomes vacant, the lieutenant-governor, who is often the chief justice of the state, can exercise the governor’s functions.

However, if a regency were to continue for a long time – perhaps years – this could become unsustainable.

The other consideration is that if there is a regency, there is no power to dismiss a governor-general. So if a constitutional crisis arose, such as that in 1975 with the dismissal of the Whitlam government, the governor-general would know that he or she could act without the prospect of dismissal on the advice of the prime minister. This unbalances the constitutional pressures that are deliberately built into the system, giving a stronger hand to the governor-general and weakening the position of the prime minister.

Read more: Australian politics explainer: Gough Whitlam's dismissal as prime minister

The problem could be addressed in the same way as the rules of succession to the throne were changed in 2015 to remove gender discrimination. It would involve each state enacting a law requesting the Commonwealth to enact a law that recognised the authority of a regent to exercise the sovereign’s powers with respect to Australia.

While it is not essential to fix this problem, it would still be wise, as a matter of orderly constitutional housekeeping, to address it before any real difficulties arise.