https://en.m.wikipedia.org/wiki/European_Union_(Withdrawal)_...
Parliament can't directly negotiate treaties with foreign powers. It's just not possible, that's a function of the executive. Parliament can approve or disapprove of such treaties but can't determine what the executive wants to do. The same goes for the referendum and is why it was a stupid idea. No referendum can require parliament or the government to want to do something, or specify exactly and unambiguously how they should go about doing something they don't want to do.
With the benefit of hindsight, it all worked out well for Johnson: he cowed the party, could renegotiate without much fear of the ultras, and could choose the circumstance of the next election to his best advantage.
The methods he chose to achieve this, though, greatly weakened parliamentary sovereignty.
Well of course I will. The system won't have changed, will it? I think you're actually accusing me of complaining just because I don't like Bojo. That's a really underhanded thing to do, and if you're going to say that, just say it straight like an adult. The rest of your comments are thoughtful and considered and part of an adult conversation; this passive-aggressive childishness really works against that.
The fact that prime ministers are answerable to parliament, and that parliament is sovereign, is IMHO the single best and most important feature of the British political system.
Contrast that with presidential systems, particularly that in the US in which the president fulfils the constitutional role of an elected George III circa 1790. Which for some reason Americans seem to think is somehow modern over 200 years later. If one of them goes off the rails you're stuck with them for years. Our leader of government serves at the discretion of our elected representatives and can be turfed out at any moment, which actually happens and isn't just a theoretical mechanism. An excellent arrangement.