Imagine a government agency that urges people to watch what they say in public, for fear of security breaches, and also hires researchers to find out exactly what they are saying. Now imagine that those “researchers” are a group of oddballs and amateurs using extremely invasive techniques. Next, throw in a campaign of harassment against a public broadcaster. Finally, add a cabinet minister who lies about some of this. When the Second World War began on Sept. 1, 1939, 75 years ago, such stuff was not imaginary and came in the form of a dubious British bureaucracy: the Ministry of Information.

As a wartime entity with the word “information” in its title, the Ministry of Information (MOI) begged for suspicion, and there was indeed a fishy history behind it. In the First World War, an institution with the same name existed, and its job was foreign propaganda. It was led by the Canadian press mogul Max Aitken (a.k.a., Lord Beaverbrook), and Aitken’s biographer, A.J.P. Taylor, says it was responsible for media-related manipulations aimed at allied and neutral countries. For the Second World War, Britain revived the MOI, but made it shadier by tasking it with “home propaganda.” Now, Britons were the targets. Also, unlike its predecessor, the MOI had trouble finding a leader...