With some questions of geography and mapping, the Romans might swear that they had it right: perhaps they had seen a particular region themselves, or, they knew people who had been there, or they had read accounts from more than one author. Even so, the state of knowledge was never perfect, as can be seen in the following unequivocal assertion of the historian Tacitus that he, at last, will be the Roman who gives ah accurate description of Britain:

Although the geographical position and the inhabitants of Britain have been described by many authors, I shall describe them once again, not to match my industry and ability against theirs, but because the conquest was only completed in this period. Where my predecessors relied on graces of style to make their guesswork, sound attractive, I shall offer ascertained fact. Britain...