Marcus Dubious said:
The only ?veto? the queen has is in regard to the swearing in of a new Prime Minister.
It is nothing more than an accepted formality and a throw back to British monarchic heritage.
But you have a point the queen could refuse to accept a new Prime Minister and therefore, technically, Britain would be without a leader.
This could possible be regarded as treason.
The idea I mentioned was covered by a BBC drama a few years ago.
Actually, she can actively dismiss the government (seeing as they are her ministers) and can dissolve Parliament, calling an early election. Britain would not be left without a leader, and even if it was, I couldn't care less - the government doesn't need to be constantly active for a country to function. In most cases it'll run itself. Pretty powerful way of vetoing something...
If she did refuse to select a Prime Minister, there would be another General Election, it would not constitute treason, seeing as that is a crime against the sovereign. Treason is defined in the Treason Act 1351 as either: "when a man doth compass or imagine the death of our lord the King, or of our lady his Queen or of their eldest son and heir"; "if a man do violate the King?s companion, or the King?s eldest daughter unmarried, or the wife of the King?s eldest son and heir"; "if a man do levy war against our lord the King in his realm, or be adherent to the King?s enemies in his realm, giving to them aid and comfort in the realm, or elsewhere"; and "if a man slay the chancellor, treasurer, or the King?s justices of the one bench or the other, justices in eyre, or justices of assise, and all other justices assigned to hear and determine, being in their places, doing their offices".
So, the monarch would either have to plot their own death or that of their family, have an affair with their own partner (again, paradoxical) or sleep with their eldest daughter (granted, disgusting but possible) or their eldest son's wife, aid the enemies of the crown or enter the service of the enemy (again, paradoxical) or kill their own ministers and judges (whereas they'd be tried for murder).