Agricola "crossed in the first ship" in 81, and defeated peoples unknown to the Romans until this time.
Tacitus, in Chapter 24 of Agricola, does not tell us what body of water he crossed, although most scholars believe it was the Clyde or Forth, and some translators even add the name of their preferred river to the text; however, the rest of the chapter exclusively concerns Ireland.
The text of the Agricola has been emended here to record the Romans "crossing into trackless wastes", referring to the wilds of the Galloway peninsula.
Agricola fortifies the coast facing Ireland, and Tacitus recalls that his father-in-law often claimed the island could be conquered with a single legion and auxiliaries.
He had given refuge to an exiled Irish king whom he hoped he might use as the excuse for conquest.
This conquest never happened, but some historians believe that the crossing referred to was in fact a small-scale exploratory or punitive expedition to Ireland.
Irish legend provides a striking parallel.
Tuathal Teachtmhar, a legendary High King, is said to have been exiled from Ireland as a boy, and to have returned from Britain at the head of an army to claim the throne.
The traditional date of his return is 76–80, and archaeology has found Roman or Romano-British artifacts in several sites associated with Tuathal.
