I never know that stupidity and coincidence can coexist in disastrous harmony.. until I read this chapter.
On a side note, I might understand why the crown prince seemingly just let the duke attack his guard. If you think about it, even if the duke managed to kill that disrespectful guard, it will just show that the duke is a terrifying person like the rumor say. The guard might die, but that also means the guard is not capable enough to save his own life; meaning he's pretty useless as a guard so why would he care?