Okay. Let me be clear. Let me try to be as clear as possible.
First of all, you're wrong in saying the conventions are no longer valid things to think about. You're absolutely wrong about that. The patriation reference case was based on conventions, and because the preamble to our Constitution states that our Constitution is similar to that of the United Kingdom, conventions still play a part. In fact, the very Office of the Prime Minister is a convention that is not entrenched in the Constitution, apart from a very, very small reference to it in one part. The whole concept of responsible government is based on convention.
So all of these conventions that have existed do continue, including the royal prerogative, including conventional restraints on executive power. However, none of them supersede the written Constitution, and in particular none of them can supersede the amending processes of the Constitution.
So where there is a conflict between any prerogative power or any conventional power and the actual details of the written Constitution, and in particular the amending processes, they take precedence.