Presenting an account of mental illness in British prime ministers from Sir Robert Walpole, generally regarded as the first to hold the position, to Tony Blair, this book reveals how depression, anxiety, dementia, and alcohol or drug use disorders have impacted British leaders over three centuries. It begins with an introduction explaining the principles of diagnosis, the methods used to assess subjects and the assignment of confidence levels in each diagnosis, and the overall significance of mental disorder in political leaders. Individual assessments then follow for each of Britain’s 51 prime ministers, revealing how evidence for psychiatric problems was found in over 70% of cases and how the prevalence of mental disorders remained relatively constant throughout the 18th, 19th, and 20th centuries.