Speaking aloud to himself, Mortimer Junior decides that only Edward's death will ensure his own safety. He fears reprisal from Prince Edward, however, so the message he writes ordering Edward's murder is deliberately ambiguous: it could also be read as ordering Edward's safety. In addition, he has ensured that the assassin—Lightborne—will be murdered once Edward himself is dead.
At first glance, the message ordering Edward's death represents the ultimate triumph of violence over language, in the sense that Mortimer has effectively made language itself into an act of violence. In using language in this way, however, Mortimer reveals his ineptitude with words: although he talks at great length about how the ambiguity of the note will protect him, Mortimer is immediately revealed as Edward's killer when the message is brought to light. Mortimer's downfall, in other words, is the result of language.
Mortimer Junior calls Lightborne in, and the two discuss the plans for Edward's murder. Lightborne scoffs at the idea that he will pity the King, and assures Mortimer that he knows many ways to kill without leaving marks on the victim's body. Mortimer accordingly gives Lightborne a letter to take to Gourney and Maltravers, along with the token that—unbeknownst to Lightborne—marks him for death.
Like the note ordering Edward's death, the murder method is meant to be undetectable. Once again, however, Mortimer proves to have no talent for covert violence: Gourney betrays Mortimer, and Edward III learns of his father's murder almost as soon as it happens.
Lightborne leaves, and Mortimer Junior takes stock of his position, which allows him to control both Prince Edward and Isabella. Gloatingly, he remarks that everyone at court fears him and hurries to do whatever he wishes. Noting that today is Prince Edward's coronation day—a day that will confirm Mortimer's own position as Protector—he brags that even fortune cannot touch him now.
Once again, Mortimer reveals the extent of his arrogance by boasting that he is immune to fortune. He also reveals himself to be more disinterested than ever in legitimate rule, since he brags that he has intimidated Prince Edward to such an extent that a mere glance from Mortimer is the equivalent of a beating in the Prince's eyes. This comment, however, also reveals Mortimer's weakness as a ruler: he relies almost entirely on force. This makes sense, given that he frequently criticized Edward II for his disinterest in warfare and bloodshed, but Mortimer's remarks about manipulating the other councilors make it clear that force alone is not enough for a successful ruler. More specifically, Mortimer also needs to be able to use language to his advantage, and the episode with the note suggests that this is not his strong suit.
Trumpets sound, and Prince Edward enters, accompanied by Isabella, the Bishop of Canterbury, and a group of nobles. The Bishop proclaims the Prince to be king, and a champion swears to defend his right to rule by force of arms.
The inclusion of the champion in the coronation—though mostly symbolic—underscores a point that Spencer Junior made earlier, in his discussion of what it means to be a nobleman: that the social hierarchy is not something that exists naturally, but that it is instead maintained by force.
As soon as Edward III is crowned, a group of soldiers bring Kent forward for judgment. When questioned, Kent admits to trying to free Edward II but insists that in doing so he was serving the true king. Mortimer Junior then orders Kent's execution over the pleas of Edward III, insisting that he does so for the good of both the king and the country. Kent himself also challenges Mortimer's right to condemn him, but is eventually escorted away under guard. Turning to Isabella, Edward III expresses concern over his own safety at Mortimer Junior's hands. Isabella, however, reassures her son that she will protect him and urges him not to think anymore about the “traitor” Kent.
Despite Mortimer's continued protestations that he is acting for the good of the country, his personal ambition is more and more obvious. Although Mortimer's position as Protector does entitle him to make decisions on Edward III's behalf, his use of the royal plural while ordering Kent's execution ("at our command") hints that he covets the throne for himself.