Yes, the monarch can assent to a change in the succession - most recently when Edward VIII assented to the Abdication Act, which forfeited his claim to the throne as well as any issue he might have had.
If the monarch could not assent to such a bill, there wouldn’t be a way to change the succession.
He’d be busy defending himself on a murder charge, which would likely be considered an incapacity leading to a new Regent being appointed.
Thank you - question answered!
Does the affected person have any right of reply? The Speaker and Lord Chancellor are political appointments, so if you got hooks into them and one other could they conspire to rule an otherwise functioning monarch as incapacitated?
By the way, here’s a good article on the Regency Acts, just so you don’t think I’m making it all up. (I have read the Acts, but it was a while ago.)
Well, they are political appointments, but in the British political tradition, the Speaker is a non-partisan position, and the Lord Chancellor (until recently) was a judicial officer. The other two officers are judges, and I think it should be assumed that the spouse of the monarch will be very protective of the monarch’s rights. I think the reason for choosing them for this purpose is that they are collectively about a non-partisan group of public officials as you could get.
The removal of incapacity is done by the same group.
The Crown, at the advice of the Regent, fails to prosecute? Worked for Richard III.
There have been many constitutional developments since then, including the principle that the monarch can not get involved in the day-to-day administration of justice. Crown prosecutors take their instructions from the DPP.
I doubt that Churchill’s depression had any impact on the succession, as he wasn’t a Royal.
Note that a major change is well underway to change some of the rules of British succession, e.g., male priority, but none of these affect the OP’s question except to note that getting everybody on board for a change in the rules is apparently still doable.
Does Parliament intend to take ALL the fun out of being regent? I mean, what’s the point if you can’t massacre your enemies?
Unless he grants a Royal Pardon to the murderer (himself).
It would be high treason, not just murder.
If the king you’re referring to was Ludwig II (“Mad King Ludwig”), it was actually stranger than that. Ludwig II had a younger brother, Otto, who presumably would have become Prince Regent once Ludwig II was declared insane in 1886…only Otto had himself been declared insane some years before. So their uncle Luitpold became regent instead. When Ludwig II died under mysterious circumstances a few days after being declared insane, Otto inherited the throne and officially became King Otto I of Bavaria. But since Otto was never considered fit to rule, Luitpold continued as Prince Regent.
Luitpold did not become senile and was never king himself. When Luitpold died in 1912 his son, also named Ludwig, became the new Prince Regent. By this time Otto had technically been king for over 25 years. Soon after Ludwig-son-of-Luitpold became regent the Bavarian parliament changed the law so that the regent could become king if the current king had been incapacitated for long enough. Ludwig-son-of-Luitpold became Ludwig III, the last king of Bavaria. He was not removed by the Treaty of Versailles, but was more or less forced to abdicate during the German Revolution of 1918-1919.
amia: Thanks for th correction. The genera concept – one guy regent for multiple disabled kings – was right; I just got details wrong.
Modern Parliaments are just wet, wobbly killjoys! 
British monarchs no longer go around granting royal pardons to whoever they feel like. They only do things on the advice of the (elected) Government.
There was a (eaked) incident where George VI had to follow his Home Secretary’s advice to sign a death warrant where he as an individual felt that commuting the sentence to life imprisonment would have been more appropriate.
Well, presumably they’re not supposed to kill people either.
Well, yes… my point was more that in Britain we seem to tolerate a level of mental instability in our leaders, so that a king with mid- to high-functioning autism might simply be seen as charmingly eccentric even though you wouldn’t necessarily want his finger on the Trident button.
Not in an official capacity, no. 