Geoffrey Wheatcroft’s books include “The Controversy of Zion,” “The Strange Death of Tory England” and “Yo, Blair!”

In 1950, a 24-year-old industrial research chemist named Margaret Roberts stood unsuccessfully as a Conservative candidate in the British general election. “We believe in the democratic way of life,” she told the voters. “If we serve the idea faithfully, with tenacity of purpose, we have nothing to fear from Russian Communism.”

At the time, Ronald Reagan was a modestly successful movie actor serving as president of the Screen Actors Guild, and a Democrat. After working in television he moved into politics, now a Republican, establishing his national reputation with a speech during the 1964 presidential campaign, much as Barack Obama did with a convention speech 40 years later. He was elected governor of California in 1966, nearly wrested the Republican presidential nomination in 1976, gained it four years later and was elected president.

By the time Reagan reached the White House, Mrs. Thatcher — as Miss Roberts had been since her marriage to an affluent and genial businessman — had achieved an even more dramatic and unlikely triumph. She entered Parliament in 1959, worked her way up the ministerial ladder and showed her steel in 1975 when she challenged and deposed Edward Heath, the woefully unsuccessful Tory leader....

...It is a remarkable story, which deserves the fresh account that Richard Aldous, a professor of history at Bard College, gives it in “Reagan and Thatcher.” His book casts new light on the heroic version in which two great leaders continued the struggle for freedom waged for generations past by “the English-speaking peoples.”...