This article challenges common understandings about the distinct features of the so-called “mixed jurisdictions”. One of the main features found in this group of legal systems, it is argued, is that they are civil-law in nature in the sphere of private law, while their public law sphere is typically Anglo-American. I argue that this may be correct as far as the structural elements of these two branches of law, for example with regard to the court structure; it may also be relevant in the context of the general, overarching values underlying both branches of law. However, as far as the detailed arrangements are concerned, a variety of set-ups reflect different types of mixes and combinations in all legal systems, including “mixed jurisdictions”: innovation, transplantation and adoption of which can be traced inter alia to global crosscutting between these two families of legal systems.This argument is developed through an analysis of the evolution of three grounds of review of the administration-unreasonableness, proportionality and legitimate expectations/ administrative promise-in the United Kingdom, the “ancestor” of the common law family of legal systems, and in Israel, currently considered a mixed jurisdiction. I show that both innovation and reliance on civil law constructs can be found in both systems just as much as common law constructs. The influence of EU law, especially ECtHR jurisprudence, renders the public law of the United Kingdom, to a certain extent, to be more civil-law-like than its so-called daughter system. Whether this mix of patterns is an unavoidable result of the irresolvable tension between exclusionism and openness, both willful and subjected, or matter that is particular to the distinct nature of administrative law and its case-by-case development in common law systems is a matter for further consideration. Clearly, though, legal reality, at least in the field studied in this article, challenges the viability of the distinction between “pure” and “mixed” legal systems.