With the news that the Prince of Wales has COVID, I’ve been asked about who might step in for the Queen if she were to fall ill as well. Under section 6(1) of the Regency Act 1937, the Sovereign can delegate their functions to Counsellors of State in the event of illness or some other indisposition. Section 6(2) of the Act states that the Counsellors must be the Sovereign’s spouse and the four individuals who are next in line for the throne and are capable of serving as a regent.
Since the Duke of Edinburgh is dead and the Duke of Cambridge’s children are too young to serve, this means the Counsellors would be Prince Charles, Prince William, the Duke of Sussex, and the Duke of York. But Prince Charles is self-isolating, Prince William is out of the country, Prince Harry lives in the US, and Prince Andrew has withdrawn from royal duties. While the Queen can discharge someone from being a Counsellor if they are absent from the UK, she can’t appoint someone else in their stead. This might seem like a potential catastrophe, but in reality, it’s unlikely to be a problem.
First of all, there is no indication that the Queen is unable to discharge her duties. But even if she were to take ill, Prince William is due to return to the UK tomorrow (and, needless to say, he could expedite his return if necessary). And although Prince Charles has COVID, that wouldn’t necessarily prevent him from acting as a Counsellor of State. While it does take two Counsellors to exercise any of the Queen’s functions, there’s no rule that says they must be in physical proximity to one another. Indeed, Prince William could sign a document in one place and then send it over to his father. And given that Privy Councils and the presentation of ambassadors’ credentials have already been conducted virtually during the pandemic, they needn’t be obstacles, either.
If Prince Charles were incapacitated by COVID, Prince Harry could potentially serve as a Counsellor as long as he is still technically domiciled in the UK. And, if necessary, Prince Andrew could serve, too. It would be awkward given the cloud that hangs over him, but it’s important to remember that Counsellors have no discretion when carrying out their functions. In the words of Sir Edward Ford, a former Assistant Private Secretary to the Queen:
They are in fact—if one may say it without disrespect to their persons—merely a piece of constitutional machinery—the nearest thing to a human rubber stamp that has perhaps yet been devised.
In extremis, a single Counsellor might even be able to act. Under section 6(3) of the 1937 Act:
Any functions delegated under this section shall be exercised jointly by the Counsellors of State, or by such number of them as may be specified in the Letters Patent, and subject to such conditions, if any, as may be therein prescribed.
Rodney Brazier has argued that this means the Queen can either allow Counsellors to act jointly “or by such number of them as may be specified in the Letters Patent,” and that number could be one. But, as we’ve seen, that theory is unlikely to be tested since there will be enough people who can serve if necessary.
 The requirements for being a regent are set out in section 3(2).
 Queen Victoria essentially went into self-isolation for many years following the Prince Consort’s death, and the Government learned to work around her seclusion. For example, Privy Counsellors would assemble outside her chamber for Council meetings while she signified her approval through a partially closed door.
 Under section 3(2) of the 1937 Act, “A person shall be disqualified from becoming or being Regent, if he is not a British subject of full age and domiciled in some part of the United Kingdom” (emphasis added). While Prince Harry currently lives in the US, it’s possible he is still legally domiciled in the UK.
 Quoted in Vernon Bogdanor, The Monarchy and the Constitution (Oxford: Clarendon Press, 1997), 49.
 Rodney Brazier, “Royal Incapacity and Constitutional Continuity: The Regent and Counsellors of State,” in The Cambridge Law Journal, vol. 64, no. 2 (July 2005), 379.