For the UK's House of Lords, reform is often characterized as unfinished business: a riddle that has been left unanswered since 1911. But, rarely can an unanswered riddle have had so many answers offered, even though few have been accepted. Indeed, when Viscount Cave was invited in the mid-1920s to lead a Cabinet committee on Lords reform, he complained of finding "the ground covered by an embarrassing mass of proposals." That embarrassing mass continued throughout the 20th century. Much ink has been spilled on what should be done with the upper House of Parliament, but much less ink has been expended on why reform has been so difficult to achieve. This book analyzes in detail the principal attempts to reform the House of Lords. Starting with the UK's Parliament Act of 1911, the book examines the century of non-reform that followed, in the process drawing upon substantial archival sources, many of which have been under-utilized until now. These sources challenge many of the existing understandings of the history of House of Lords reform and the reasons for success or failure of reform attempts, arguing against the popular idea that the 1911 Act was intended by its supporters to be a temporary measure. The book will be of interest to all those working in constitutional law, as well as those with an interest in legal history. (Series: Hart Studies in Constitutional Law - Vol. 1)