The mysterious life and career of Desmond Morton, Intelligence officer and personal adviser to Winston Churchill during the Second World War, is exposed for the first time in this study based on full access to official records. After distinguished service as artillery officer and aide-de-camp to General Haig during the First World War, Morton worked for the Secret Intelligence Service from 1919-1934, and the fortunes of SIS in the interwar years are described here in unprecedented detail. As Director of the Industrial Intelligence Centre in the 1930s, Morton's warnings of Germany's military and industrial preparations for war were widely read in Whitehall, though they failed to accelerate British rearmament as much as Morton - and Churchill - considered imperative. Morton had met Churchill on the Western Front in 1916 and supported him throughout the 'wilderness years', moving to Downing Street as the Prime Minister's Intelligence adviser in May 1940. There he remained in a liaison role, with the Intelligence Agencies and with Allied resistance authorities, until the end of the war, when he became a 'troubleshooter' for the Treasury in a series of tricky international assignments. Throughout Morton's career, myth, rumour and deliberate obfuscation have created a misleading picture of his role and influence. This book shines a light into many hitherto shadowy corners of British history in the first half of the twentieth century. This book will be of great interest to scholars and informed lay readers with an interest in the Second World War, intelligence studies and the life of Winston Churchill.