How to Win An Information War, the new book by Peter Pomerantsev, is a riveting biography of Sefton Delmer, the German-born, Berlin-educated, British newspaperman who first interviewed Adolf Hitler for the British press while accompanying him and his inner circle on pre-1933 Nazi election campaigns.

But as Pomerantsev’s book reveals, there was something ultimately far more historically significant – and colourful – about Sefton Delmer. In a nutshell, he was, until today, a long forgotten hero, who mastered the art of “Black Propaganda” during the Second World War.

Until I began writing my latest book, The Wizard of Fleet Street…and Me, I had never heard of Sefton Delmer. I happened on him accidentally while researching the wartime exploits of another British journalist and editor, Harold Keeble – the eponymous “Wizard” of my book.

I learnt that Sefton Delmer had set up the Daily Express bureau in Berlin in the early 1930s, before Hitler came to power. In 1933 Delmer left Nazi Germany to head British newspaper offices in Spain and elsewhere in Europe. Back in London at the start of WWII, Delmer was eventually recruited into the Secret Services, along with Ian Fleming. Osbert Lancaster, Richard Crossman and Leonard Ingrams – father of Private Eye founder Richard Ingrams. With his fluent German, Berlin accent, and intimate knowledge of the Third Reich, he was ideally placed to create and disseminate “Black Propaganda” – in other words fake news – to mislead and confuse Nazi troops while denting their morale.

And it was in the depths of this clandestine world that Delmer joined forces with his dashingly handsome young Daily Express colleague, Harold Keeble.