In 1974 Sir Leslie Scarman, in delivering the twenty-second Hamlyn lecture, proposed a written Bill of Rights for the United Kingdom that would be “entrenched” and hence binding on Parliament even without a written constitution. (Entrenchment is sometimes used to describe a process whereby an Act of Parliament incorporates a Bill of Rights but provides that any subsequent legislation will be deemed to be in compliance with that Bill unless it clearly manifests a contrary intention.) The controversy and constitutional commentary surrounding Scarman’s proposal in the 1970s continues to have relevance for the nature of the British constitution. Historically and still today theoretically, the unwritten British constitution rests on the principle of parliamentary sovereignty and the implication that Acts of Parliament are not subject to judicial review and that judges must adhere to the last expression of Parliament.This article suggests that entrenchment is not possible because it creates fundamental law by an Act of Parliament, something that for all its authority Parliament cannot do. Entrenchment attempts to alter fundamentally the structure of government without a corresponding change in constitutional premises. Proponents of entrenchment seek to achieve constitutional change without discarding the traditional theory of parliamentary sovereignty. Obviously, constitutional reforms would fare better if they were compatible with the orthodoxy associated with A.V. Dicey’s view of the British constitution, that the last expression of Parliament is the supreme law of the land. Unfortunately the essence of fundamental law and the nature of entrenchment force a conflict between theory and reform. Proponents of entrenchment advanced numerous arguments and precedents supposedly offering constitutional justification, seeking to reconcile the theoretical demands and implications of parliamentary sovereignty with entrenchment. Entrenchment, however characterized, involves a fundamental alteration of the legal and political order. An entrenched provision would serve the same function as a written constitution: law that the legislature could not change save by specified amendment. As fundamental law it must derive its existence from the ultimate source of legitimate authority – those governed – and not simply by legislative fiat. For entrenchment to be effective requires some form of explicit consultation with the people.The passage of the Human Rights Act of 1998 and the creation of a Supreme Court for the United Kingdom that began operating in 2009 have raised the specter of judicial review and challenges Britain’s constitutional legacy of parliamentary sovereignty. The Human Rights Act was passed to rectify the oddity that a British subject whose rights under the European Convention of Human Rights were being violated could not get legal redress in a British court, but had to seek relief from the European Court of Human Rights in Strasbourg. The Act requires judges to interpret all legislation as compatible with the Convention to the extent possible. If the legislation cannot be interpreted consisted with the Convention then the courts may issue “a declaration of incompatibility,” but the statute remains in force until and unless Parliament decides to alter the statute. Thus, parliamentary sovereignty remains theoretically intact.The tensions and ongoing debate over the nature of the British constitution reflect the desire to place human rights and liberties beyond the control of Parliament while still acknowledging the sovereignty of parliament.