page 146 of 960 of Sir Thomas Malory: Le Morte Darthur: The Definitive Original Text Edition

146:

If Arthur does not pay there will be war. Arthur also has to promise to protect the messenger’s lives on their return journey to the emperor because he’s a good king. By the way, Arthur is not about to pay Lucius tribute, especially since he believes he’s as powerful (and descended) from the great emperors of Rome (as a lot of rulers used to think – and still might in the 21st century)