Mr. Bruff is the family lawyer for the Verinders. He's known them forever – since before Rachel was even born. He was friends with Rachel's father, the late Sir John Verinder, and has stayed friends with Lady Verinder after Sir John's death. And he helps Rachel out after her mother dies. He's a trustworthy lawyer and a loyal friend.
But what else do we know about him? Well, his name actually tells us a lot! "Bruff" sounds like a combination of "brusque," and "rough." "Brusque," of course, means that he is abrupt, blunt, and straightforward – almost to the point of being impolite, sometimes. Yep, that sounds like Mr. Bruff. And "rough" suggests that he's not a cuddly guy. This is true, but beneath that "rough" exterior, Mr. Bruff cares a lot about Rachel and is willing to do almost anything to help her figure out the mystery of the Moonstone and be reconciled with Franklin Blake.