Tacitus, a Roman senator writing in the early second century, composed the Annals, a history of the emperors from Tiberius through Nero. This is Book 11. Books 7 through 10 are lost, and with them Caligula’s whole reign. The narrative resumes in Claudius’s Rome, capital of an empire now run by one man rather than the old Republic of a senate and elected officials.

Claudius is a scholarly emperor who can be led. Freedmen, former slaves in the palace, outrank consuls — the two officials once elected to run Rome for a year. Narcissus and his rivals control access. Messalina, his wife, stages a mock marriage to Gaius Silius while Claudius is at Ostia, Rome’s port; when the household finally tells him, she is executed. Britain gives this unmilitary man a conqueror’s mask. Men of rank from Gaul, today’s France and neighbors, are argued into the Senate, and citizenship widens. It is a court story: who holds the door holds the state.