I'd be interested to get others' opinions of
this analysis by three constitutional scholars on the question of what must happen next to trigger Brexit.
My tl:dr summary of what they are saying is as follows:
1. Article 50 can only be invoked in line with the constitutional requirements of the member state wishing to leave.
2. The UK constitution provdes two potential mechanisms for invoking Art. 50: an Act of Paliament giving the PM the authority to do so, OR the exercise of the Royal Prerogative.
3. The exercise of the prerogative in these circumstances would overturn centuries of well-established legal precedent that says prerogative powers must NOT be used to overturn statute - the statute in question here being the European Communities Act of 1972.
The ramifications of the PM using the prerogative and triggering Art. 50 without an Act of Paliament - the ramifications, that is, for parliamentary sovereignty and the separation of powers - are so vast (and chilling, if you really think about it) that they dwarf the Brexit decision.
I haven't paid any attention to constitutional law since 1st yr law school,

so would be interested to hear what the other legal brains here make of it.