Don't know the source for this anecdote, quoted in The Guardian.
In the 16th century a pirate chieftainess, Granuaille, controlled the adjacent seas. She became so annoyed by the English officials that she took ship, sailed up the Thames to complain to Elizabeth I. Neither knew the other's language, Granuaille speaking Irish and Elizabeth English, so they conversed in Latin, the then lingua franca. A good story.