Mr. Simms is the author of "Three Victories and a Defeat: The Rise and Fall of the First British Empire, 1714-1783."

In "Witness to History," Victoria Schofield remarks that her biographical subject, the British historian John Wheeler-Bennett (1902-75), was "never a household name" but that, by the mid-20th century, "he knew virtually everyone who was." And so it seems. He knew the Nazi-era German diplomat Adam von Trott, who was later executed for conspiring against Hitler. He knew Franklin Roosevelt, whose 57th birthday party he attended in 1939. He was in regular contact with British statesmen, especially Harold Macmillan and Anthony Eden. For good measure, he supervised John F. Kennedy's undergraduate thesis at Harvard. He met with several Bolshevik leaders, too. There are not many men who could tell an undergraduate who was undecided between Jesus Christ and Leon Trotsky that, although he himself had never met our Lord, he "did have a long talk with Trotsky and I don't think I should advise you to follow him."

As Ms. Schofield shows, Wheeler-Bennett was one of the first of a new class of "experts" who emerged after the peace settlement that concluded World War I. As a young man in the interwar years, he set out to make himself an authority on international affairs generally and on Germany in particular. Serving in the early 1920s as an assistant to Gen. Neill Malcolm, then a kind of roving British ambassador, he traveled extensively, from Germany and the other parts of Continental Europe to North Africa and the Far East.

The first chapters of Ms. Schofield's engaging chronicle evoke a lost imperial world. In Cairo, she tells us, Wheeler-Bennett stayed at the Shepheard's Hotel, a "famous caravanserai" where one "could not sit for half an hour on [the] terrace without meeting at least half a dozen friends and acquaintances." At another time we see Wheeler-Bennett chasing smugglers in Borneo. It was in Berlin that, having left Malcolm's staff, he chose to settle in the late 1920s and early 1930s....