Pliny, Letter 10.78

1Such is the situation of the city of Byzantium, with a crowd of travellers flowing into it from every side, that, in keeping with the custom of earlier times, we have thought it right to support its magistrates with the protection of a legionary centurion. 1If we decide that the people of Juliopolis should be helped in the same way, we shall burden ourselves with a precedent; 2for more cities will make the same request, the more so the weaker they are. 2I have such confidence in your diligence that I believe you will take every measure to ensure that they are not exposed to wrongs. 3If any people behave contrary to my discipline, let them be restrained at once; 3or, if they commit offences too great to be adequately punished on the spot, if they are soldiers, you will make what you discover known to their commanders, or, if they are travelling on towards Rome, you will write to me.