One of the central actions that occur in this final scene is the execution of Buckingham, which in itself raises a number of very interesting themes that dominate the play. Note the way that as he is brought to be executed, Buckingham begins to think of repentance and recalls past actions and prophecies. Buckingham in particular remembers Margaret's curse and how true it has turned out to be. Although it was dismissed as the ramblings of a mad woman before, Buckingham is forced to recognise that it speaks truth and has accurately prophesied what has happened, which leads him to conclude that he deserves punishment. The element of prophecy indicates the theme of God being in control, and thus the theme of moral justice for those who give themselves over to evil (such as Buckingham and Richard) clearly is raised, which in turn foreshadows the fall of Richard's evil regime. Note very carefully how Buckingham draws attention to God's justice and how it will be triumphant in the world of men in the following lines:
Thus doth he force the swords of wicked men
To turn their own points in their masters' bosoms.
Buckingham is arguing that those who give themselves over to evil will meet their own end because of their wickedness. Thus Richard, having dedicated his life to wicked deeds, will find that his life and his reign will be cut short precisely as a result of his evil nature. This acts as something of an aphorism in the play, that foreshadows the defeat and death of Richard and establishes the theme of God's justice and how he deals with evil.