Winston Churchill’s last major speech as British prime minister, delivered to Parliament on March 1, 1955, was one of his best. In vivid terms, Churchill made the case for nuclear deterrence, reflecting on the “sublime irony” that the world had reached a point “where safety will be the sturdy child of terror, and survival the twin brother of annihilation.” In this terrific book, Farmelo tells the story of the United Kingdom’s nuclear program, which began with pioneering work in Cambridge before World War II and ultimately merged with the United States’ Manhattan Project. The book is built around a compelling portrait of Churchill that demonstrates the variability of his judgment. Farmelo also introduces readers to the remarkable collection of scientists who led the British endeavor and who helped shaped the country’s nuclear policy, including Frederick Lindemann, Churchill’s main scientific adviser, whom Farmelo portrays as an antidemocratic snob with flawed judgment. Farmelo demonstrates that although principles and evidence often shape the relationship between science and policy, personality and politics play just as large a role.