Who is Sir Humphrey Marlow from The Prince and the Pauper and what is their importance?

Humphrey Marlow is the Prince of Edward's whipping boy. His job is to take beatings for the prince when the prince fails to perform well at his studies. Humphrey becomes a confidant of Tom, who he thinks is the prince. Thinking that he is helping the prince to regain his lost senses, Humphrey tells Tom much about how the court functions, which is very useful to Tom.