A few days after Joffrey's arrival,
Cersei goes to the IPD office and talks to Vimes. She tries to gain his sympathy and extra protection for her son, but both backfire pretty spectacularly. But Vimes does assure her that Joffrey will be as protected as any other person on the island.
Later that day, Vimes
has a chat with Ned Stark. Vimes tells Ned about the conversation and asks him not to take the law into his own hands, as it were. Ned agrees, even though he doesn't like it, and promises to pass the message onto his family.