Carol Ann Duffy's "Havisham" is spoken from the perspective of Miss Havisham, the vengeful spinster who was jilted at the altar in Charles Dickens's novel Great Expectations. That the poem's title refers to her only as "Havisham," rather than "Miss Havisham," perhaps hints that she wants to get rid of any reminder of her singleness (or that she has become too old for the title "Miss," which typically connotes a younger woman).
In the poem, as in the novel, she clearly hasn't been able to move on from this experience. These opening lines establish her simultaneous rage, hatred, and lingering love toward the man who abandoned her. In the poem's first line, for example, Havisham refers to her former fiancé using the phrase "Beloved sweetheart bastard." This is an oxymoron: the positive, romantic words "Beloved" and "sweetheart" contrast with the derogatory "bastard." By describing her lover in such paradoxical terms, Havisham expresses both anger and heartache at the same time: she is furious with this person, but she still, it seems, loves him.
The alliterative /b/ sounds in "Beloved" and "bastard" are piercing and harsh, reflecting the intensity of Havisham's conflicting emotions. The firm, full-stop caesura after the word "bastard" makes the speaker's rage sound firmer and more forceful still.
Havisham goes on to claim, "Not a day since then / I haven't wished him dead." In other words, her fiancé's abandonment has left her so angry and full of hatred that she wants him to die. And yet, the enjambment between lines 1 and 2 allows the phrase "I haven't wished him dead" to stand on its own visually. In this way, the poem subtly illustrates how even within the vengeful, violent rage that Havisham feels toward her former lover, a tender, sorrowful desire for his wellbeing, and perhaps even his return, still remains.