Belloc focuses primarily on those figures who changed the course of English history, analyzing their strengths, mistakes, motives and deeds.

With brief and vivid chapters, Belloc paints the portraits of Henry VIII, Anne Boleyn, Elizabeth I, Thomas More, Mary Tudor, Thomas Cromwell, Mary Stuart and many others. He illustrates how the motives of Protestant leaders were rarely religious in nature, but usually political or economic.

Belloc, who served in Parliament from 1906 to 1910, underscores his study of these powerful personalities with the fact that Christendom was once a single entity under the authority of the Catholic Church. Until the Reformation, he argues, each country viewed itself as a part of the whole.

Many European princes, however, resented the power of the Pope. The Reformation, aided by the rise of nationalism, was a means for them to shake off Papal authority and to rule their territories independently. It also gave European monarchs control over the Church and its property in their realms, including the taxes that would normally be sent to Rome.