The purpose of this book is to put the achievements of Agricola's navy, apparently understated by Tacitus, in their true perspective, with the proposition that the Roman fleet reached the furthest limit of the known world, Thule, or Mainland, Shetland, where it located a convenient anchorage, possibly in Lerwick harbour. To support this theory, firstly the identification of Thule as Shetland during the classical period from the time of Pytheas onwards is investigated through collation of geographical sources, secondly the earliest manuscript of Tacitus' Agricola comes under closer scrutiny at the relevant points than ever before, and finally contemporary literature is reassessed to determine the significance of Caledonia and Thule in the Flavian propaganda machine and to suggest the first Roman presence in the Shetland Islands.