This book is the first analysis of political defections over a long time span. It investigates all the Liberal/Liberal Democrat MPs and former MPs who defected from the party between the elections of December 1910 and May 2010 - around one sixth of all those elected - as well as the smaller number of inward defectors. Each of the 122 defections was an expert judgment on the state of the party at a specific date. The research investigates the timing and reasons for all the defections and reveals long-term trends and underlying causes and apportions responsibility between leaders for them. The author finds some significant differences which distinguished defectors from loyalists and draws wider conclusions about the underlying factors which lead MPs to defect. This book will be of interest to students and lecturers of British politics and anyone interested in the relationship between British political parties in the last century.