Public Law: Text, Cases, and Materials (2019, 4th edition), page 316:
Moreover, since Wade says that prerogative decisions must affect rights, he argues that a decision by the UK government to commit the United Kingdom to an international treaty would not be an exercise of prerogative power: entry into treaties cannot, by itself, alter rights in domestic UK law. Similarly, according to Wade, the granting of passports is not a prerogative power, because ‘[a] passport has no status or legal effect at common law whatever’.28
Footnote 28 refers to page 58 in Sir William Wade's Constitutional Fundamentals, revised edition (1989, London: Stevens and Sons). The University of Toronto has just one copy, but I don't live near it and it charges $20 for interlibrary loans.