Plutarch (c. AD 46 – after AD 119) was a Greek Middle Platonist philosopher, historian, biographer, essayist, and priest at the Temple of Apollo in Delphi. He is known primarily for his Parallel Lives, a series of biographies of illustrious Greeks and Romans, and Moralia, a collection of essays and speeches.

References to Roman Britain from Plutarch’s Caesar Chapter 23

[2] His expedition against the Britanni was celebrated for its daring. For he was the first to launch a fleet upon the western ocean and to sail through the Atlantic sea carrying an army to wage war. The island was of incredible magnitude, and furnished much matter of dispute to multitudes of writers, some of whom averred that its name and story had been fabricated, since it never had existed and did not then exist; and in his attempt to occupy it he carried the Roman supremacy beyond the confines of the inhabited world.

[3] After twice crossing to the island from the opposite coast of Gaul and in many battles damaging the enemy rather than enriching his own men—for there was nothing worth taking from men who lived in poverty and wretchedness— he brought the war to an end which was not to his liking, it is true; still, he took hostages from the king, imposed tributes, and then sailed away from the island.