Recording secrets under orders

This book is a goldmine of once highly secret intelligence material: the diary kept, night by night, by the head of the counter-espionage branch of the security service, MI5. Diaries were forbidden to British combatants (though, luckily for historians, the chief of the general staff, among others, broke his own rule, and kept a long one). A special exception was made for Guy Liddell, who was ordered to keep one by his director-general. Here is the result as dictated nightly in the office, and kept for over 50 years in successive director- generals’ office safes, codenamed ‘Wall-flower’; now released to the national archives at Kew.

It disposes at once of any idea that a senior MI5 official was any sort of idle staff officer, quietly embusqué away from the battle. Liddell’s hours were clearly long, and the variety of subjects he had to cover almost inexhaustible. The Luftwaffe’s onslaughts on London made no mark on his even temper. Unlike most diaries, there is nothing here about his private life (he was separated from his wife, who lived with their four children in California); but plenty about his work. There were six divisions in MI5, lettered from A to F ; his was B, and the editor cites 20 sub-branches. Liddell kept a close eye on T. A. Robertson’s sub-branch, B1(a), which ran back — with, in the end, astounding success — almost all the agents the Germans thought they had implanted in the United Kingdom. The earliest stages of this now famous double-cross system can here be explored in detail. It needed perpetual discretion: the slightest slip, and the Germans might rumble everything.