Victorian prologue: MID, NID and the special branch -- Spies and spy scares: the birth of the Secret Service bureau -- Room 40: the rebirth of British codebreaking -- Secret intelligence on the western front -- Counter-espionage and counter-subversion: M15 and the special branch -- 'Adventure and romance in the Secret Intelligence Service in red Russia": the failure of covert action -- The red menace at home -- The Irish débâcle -- GC & CS, SIS, and Anglo-Soviet relations 1920-1924 --Zinoviev letters and the breach with Russia -- Depression: the MacDonald years -- Appeasement: the road to Munich -- Rumours of war and war -- Winston Churchill and the making of the British Intelligence Community -- Epilogue: war and peace