Legal background
The 1937 Act makes provision for when a Sovereign is unable to perform Royal functions by establishing when a Regency or Counsellors of State may be needed. Under the 1937 Act:
A Regency would occur where a Sovereign succeeds to the throne under the age of 18, or where a Sovereign is totally incapacitated ("by reason of infirmity of mind or body") or "is for some definite cause not available".
Counsellors of State can be delegated Royal functions in circumstances falling short of those giving rise to a Regency – namely if a Sovereign is ill (but not so ill as to warrant a Regency) or absent from the United Kingdom.
	Section 6(1) of the 1937 Act confers a power on the Sovereign to delegate Royal functions to Counsellors of State "in order to prevent delay or difficulty in the dispatch of public business" in two circumstances. Those circumstances are: (1) "illness not amounting to such infirmity of mind or body as is mentioned in section two of this Act" (which deals with a Regency) and (2) "absence or intended absence from the United Kingdom". The delegation is made by the Sovereign by Letters Patent for the period of the illness or absence. The Sovereign may revoke or vary the delegation by Letters Patent.
	Section 6(1) expressly places a restriction on the functions that may be delegated: "no power to dissolve Parliament otherwise than on the express instructions of the Sovereign or to grant any rank, title or dignity of the peerage may be delegated." Aside from this, the Sovereign can specify in the Letters Patent which functions are (and are not) delegated. For example, Letters Patent have previously stated that Counsellors of State cannot approve and sign Letters Patent that signify Royal Assent to Acts of Parliament which touch on the Act of Settlement or the Sovereign’s style and titles. In practice, when Counsellors of State were appointed during Her Majesty Queen Elizabeth’s absence from the United Kingdom, the Letters Patent included separate schedules detailing those functions which were delegated and those which were not. In the case of the State Opening of Parliament by Counsellors of State in May 2022, the Letters Patent simply delegated that particular function.
	If no individuals have been added by name via separate primary legislation, the Counsellors of State consist of (and are restricted to) the spouse of the Sovereign and the four persons who (excluding those who are disqualified - see paragraph 11 below) are next in the line of succession to the Crown or, if there are less than four, all of those persons.
	Any person disqualified from acting as Regent is also disqualified from acting as a Counsellor of State. The disqualifying factors are: (1) not being a British subject of full age1 and domiciled in some part of the United Kingdom2; (2) under section 2 of the Act of Settlement 1700, being incapable of inheriting, possessing and enjoying the Crown (as a result of Roman Catholicism), or (3) being disqualified under section 3(3) of the Succession to Crown Act 2013 from succeeding to the Crown as a result of marrying without the consent of His Majesty.
	The Regency Act 1943 amended section 6(2) of the 1937 Act to allow any person who would be required to be a Counsellor of State to be excepted from among the number of Counsellors of State during their absence from the United Kingdom. There is, however, no provision for a substitute Counsellor of State to be appointed.
	The Regency Act 1953 provided that Queen Elizabeth, the Queen Mother, be a Counsellor of State as she was otherwise no longer a Counsellor of State following the death of King George VI in 1952.
	When the Sovereign wishes to delegate Royal functions to Counsellors of State, the functions are required to be delegated to all Counsellors of State (unless any Counsellors of State are excepted for the period of any absence or intended absence from the United Kingdom during the whole or any part of the period of delegation). Section 6(3) provides that any delegated functions must be "exercised jointly by the Counsellors of State, or any such number of them as may be specified in the Letters Patent, and subject to such conditions, if any, as may be prescribed". In practice, therefore, a delegation of functions via Letters Patent creates a pool of Counsellors of State and then usually specifies that Counsellors of State are required to act in pairs. In the case of the State Opening of Parliament by Counsellors of State in May 2022, the Letters Patent appointed three Counsellors of State (as the Duke of Sussex was excepted due to his absence from the United Kingdom) but then specified that the cause of summons (i.e. the Queen’s speech) be "declared by one Counsellor of State in the presence of another".