Earlier quoted context omitted.
In theory, no - the doctrine of Parliamentary sovereignty holds that there are no checks on the power of Parliament, which is absolute. So if it chooses to have someone's head removed for spurious reasons it does in principle have the power (this would be an Act of Attainder, not used since the 18th Century, I think, and held to be so oppressive it's outlawed specifically in the US Constitution). In practice, it's qu…
Interesting, thanks for explaining stuff I didn't know. Is it concerning to people in the UK that the parliament has supreme power? What if an evil tyrant and her party had control of parliament, couldn't she make herself dictator for life? (I don't mean PM May, I mean in general :-)).
1) Parliament is supreme, not the PM. So extreme acts require the consent (in advance) of both the Commons (which has a built-in government majority but does sometimes have its own opinions - see Brexit) and the Lords (which can be unpredictable).
2) Norms are powerful in the Westminster system (sometimes in the form of so-called constitutional conventions) and surprisingly effective at stopping bad behaviour.
3) We've developed fairly strong judicial review, so the courts restrain illegal behaviour by the government. Although the law can be changed, it turns out this still stops a lot of abuses.
4) The evil PM would still have to successfully govern, which requires either the consent of the governed or massive force (at which point they'd need the active support of the military as well, and the military in Britain have stayed out of active politics since the 17th Century - another strong norm).
5) The Queen retains reserve powers, including the right to veto bills (she's theoretically the third 'house' of Parliament). She probably gets to do this exactly once before being deposed, and an attempted auto-coup is one of the more likely outcomes.
It's an odd system, but historically it actually works well. I spent some time interning in the US Congress expecting to find the system much better than ours, but I came away believing that a strong separation of powers in a Presidential system may create more problems than it solves.