LitCharts assigns a color and icon to each theme in The Once and Future King, which you can use to track the themes throughout the work.
Chivalry, Satire & Medieval Life
Fate (Time)
Quest and The Holy Grail
Might vs. Right
War
Summary
Analysis
Uncle Dap and King Arthur begin to notice that Lancelot and Guenever are falling in love. Arthur had been warned of this by Merlyn, but had never truly paid attention to his warnings. Unsure what to do, Arthur decides to take Lancelot with him to the Roman War to get him away from Guenever. The Roman War is a long and arduous conquest that is ultimately successful—Arthur is recognized by Rome as the overlord of England—and the pair return to Camelot after two years, determined not to let Guenever come between their friendship.
Although Arthur had been warned of Lancelot and Guenever's relationship—as well as many other things—by Merlyn, he chooses to ignore it. This choice is fundamental to the tragedy and fate of the characters; by choosing to ignore premonitions, by seeking to ignore fate or refuse to allow it to destroy what he is trying to build, Arthur simply plays into the path destiny has given him.