Responses

True. And let's be honest.
Like Arth said, deep down Payne always feel the hatred (or annoyed at least) towards his father and other royals. He hates the doctrine they gave him. He knows his brother never worth the throne.
Payne needs advisor like Arth who speaks nothing but truth. Eventho it hurts and risky.
I dont think Payne will let Arth be his advisor when he ascends the throne, if Arth really did poison the king. That would just put Payne on edge and make him paranoid.