In this new paper for Policy Exchange’s Judicial Power Project, Professor Martin Loughlin of the LSE outlines the failings he perceives in the Supreme Court’s recent prorogation judgment. The paper is framed as the judgment on appeal by an imaginary higher court, which helps to isolate and highlight the Supreme Court’s missteps, central amongst which is its inattention the significance of the Crown in our constitutional scheme and its history. The paper opens with an introduction summarising where and why the Supreme Court went wrong.