Dobb was unusual. Though a more moderate socialism did come to hold political sway in Britain, the nation consistently rejected the extremist politics that swamped the rest of Europe. Even at the outbreak of World War II, Communist and fascist parties counted their combined memberships at around 40,000 — less than one percent of the population — and few of those were active. In 1933, Wyndham Lewis’s sympathetic biography of the new German chancellor, Adolf Hitler, was displayed in a famous bookshop on London’s Charing Cross Road. Twice a day, the window had to be hosed down to remove all the accumulated spittle.

While British politics remained resolutely mainstream, science flirted with the fringes. Social hygienists recommended that girls eat cakes and porridge to avoid sexually awakening themselves. Psychoanalysts applied their theories to “the insanity of nations.” Eugenicists claimed that a “defective” generation was being bred, arguing that criminality as well as physical and mental characteristics were inherited via “germ plasm.” Those classed as defective could include vagrants, inebriates, drug addicts, prostitutes, perverts, imbeciles, deaf-mutes, the blind, the insane and epileptics — totaling, in one estimate, 9.5 million people, almost one-quarter of Britain’s population. The birth control pioneer and eugenicist Marie Stopes, concerned with the decline in what she called the “imperial race,” disowned her own son because he married a woman who wore spectacles.

The outbreak of the Spanish Civil War in 1936 pitted the democratic republic against nationalist authoritarians. The conflict made a profound impact on Britain — one which, as Overy rightly says, has often been underrated. His chapter on it is one of the most affecting sections of the book, telling of how 4,000 Britons — scientists, philosophers, poets and manual workers alike — volunteered to fight Fascism in a country to which they had no connection, simply because they believed it to be a just cause. George Orwell was among those who went, hand grenades dangling from his belt, accompanied by a small dog with the initials of the Marxist party to which he belonged painted on its side. Orwell, Overy says in the course of a particularly winning description, was “so fastidious about completing his toilet each day that if there was no water to shave in, he would shave in wine.” That certainly brings a whole new dimension to Champagne socialism. Orwell was wounded in action, shot through the neck by a nationalist sniper. He was lucky to survive. Many did not.

Such had been the horrors of World War I that pacifism, and the avoidance of war by any means, was a dominant theme of the interwar years. The Spanish Civil War and the enormities of the Nazi regime in Germany changed that. “I hate war with as much venom as you do,” the novelist Storm Jameson wrote to her pacifist colleague Vera Brittain, “but I have come to believe that there are certain values for which it may be necessary to fight.” When the crisis of civilization really did arrive in the shape of World War II, there was no choice about how to deal with it. Britain fought for its liberty and its life.

“The Twilight Years” was published in England as “The Morbid Age.” Overy notes that Leonard Woolf was obliged to retitle some of his books for American publication: “Barbarians at the Gate” became “Barbarians Within and Without,” and after some debate “Quack Quack,” his critique of capitalism, became “Quack-Quack,” with a hyphen. These may be trifling, but Overy’s British title is more memorable and more appropriate to the content than the American one. It is hard to see why a publisher would prefer “The Twilight Years” — unless putting the word “Twilight” on the cover is enough to persuade Stephenie Meyer’s audience of teenage vampire fans to buy scholarly British cultural history.