Yes, but she can also be declared crazy by a couple of judges and the Speaker of the House of Commons, and replaced by a regent who could give it assent. If the regent won’t budge, the same process can bump the regent out and move on down the line, all the way to Karen Vogel if need be.
When George III became ill, they basically just forged his assent to the legislation establishing a regency, so there’s always that option.
If a non-British citizen were to be appointed PM, would they necessarily and automatically become British? Would they have to be naturalized before taking office? Iirc there is some precedent in the laws of some Commonwealth countries that allows one to hold office as a non-citizen as long as one is a citizen of another Commonwealth country (e.g. Canadian citizen as PM of Australia), but I don’t think that applies to Americans (since the US is not a member of the Commonwealth), unless they are a dual citizen or something.
There was an interesting hypothetical a while back as to the certainty of the paternal line. Iirc it is accepted in a genealogical perspective that there are significant chances (maybe a 10% chance per hundred years or something?) that a person’s documented patrilineal line is fictitious due to adultery, baby-swapping, or other shenanigans. Some have speculated that the heir apparent could have been accidentally swapped for a commoner’s baby by a nurse in the 1600’s, and the royal baby grew up in poverty and emigrated to the colonies, and the true King of Great Britain, etc. is a homeless guy in NYC descended from him. Of course, there’s no actual evidence for this, but it makes a good story.
I doubt this matters. Until very recently, when a married woman had a child there was an irrefutable presumption that her husband was legally the father of the child, and the child had all of the rights and privileges of being his child.
So adultery wouldn’t matter, but baby-mixups are a question I’m not sure about. Since babies weren’t born in hospitals until recently, I doubt it even happened, but I don’t know if the common law would have dealt with that. In most U.S. states today, they assume a form of equitable adoption after a period of time, and no swapping 8 year olds back to their biological parents. That would be terrible.
No, a non-British citizen appointed PM wouldn’t automatically become British. Current convention is that the PM should be a member of the House of Commons, which means they must be a citizen of the UK, Commonwealth, or the Republic of Ireland.
I’m not sure what would happen if the Monarch decided to appoint Charles Manson who, obviously, meets none of these requirements. The law says little on the subject of deranged lunatics, presumably to avoid unnecessarily depleting the pool of available candidates.
Andrew Bonar Law was born in New Brunswick and eventually became Prime Minister of the UK. However, this was back when everyone born in British colonies were British subjects, and there was no such thing as Canadian citizenship.
Not necessarily. Her Majesty’s powers in each Commonwealth realm will depend on the constitution of each realm. In some cases, the constitution if a Commonwealth realm provides that the Governor General has independent powers that the Queen cannot exercise directly.