This chapter considers the origin and evolution of English administrative law principles in Singapore. It discusses the reasons behind the initial adoption – almost wholesale – of English administrative law on Singapore’s independence. The chapter analyses how English administrative law principles of judicial review were used to maintain a predominantly “green light” approach to judicial review until very recently. However, since 2013, the courts have adopted a stronger and more involved approach to reviewing executive decision-making. This includes, expanding judicial review to areas of executive decision-making that were previously non-justiciable (for example, the exercise of clemency powers and decisions involving national security interests); incrementally removing restrictions on standing; questioning the validity of ouster clauses; and expanding the scope of substantive review. While these developments mirror those in the English context, the chapter looks at the reasoning and principles utilised by the Singapore courts to make these changes to their jurisdiction. It highlights how the courts have moved away from the use of English law or, indeed, other common law jurisdictions for inspiration. Instead, there is a strong emphasis on building autochthonous local lines of precedent that better reflect the constitutional and political environment of Singapore. An analysis of the courts’ reasoning shows how the recent assertion of a stronger role by the courts is not based on a distrust of public power (as is the case in other common law jurisdictions). Rather, the courts have stepped up the scope of their review because of a perceived need on the part of the courts to contribute, as a ‘co-equal’ participant, its’ unique institutional perspective on matters of governance and accountability. The chapter concludes with a discussion of the localised contours of the separation of powers doctrine that are likely to drive the future development of judicial review principles in Singapore.