Hard Border likely according to leak of UK government documents

[Denzil_DC]

6. The UK parliament is sovereign.

The queen won't "fire" a prime minister on her own initiative. She responds to the situation in parliament, where the leader who can garner the most support among MPs (most often but not always the largest party) presents him or herself to the queen to be appointed.

She has a constitutional role in appointing a prime minister (it's unthinkable that she would veto a contender who commanded the support of the majority of MPs), but there are arguments among constitutional scholars about whether she has the power to dismiss Johnson if, for instance, a vote of no confidence went against him in parliament but he decided not to resign. It's a situation she and her entourage would strongly resist her being put in.