The mind may need a little preparation for the term "Troll lawyer". Vampires, obviously; Dwarfs are argumentative and much inclined to strict rules; there is a well-known Zombie, but a Troll with an argument more sophisticated than a club? Well, Mr Thunderbolt is not the average Troll. He's the nephew of the Diamond King and diamond himself. He has articled at Morecombe, Slant and Honeyplace and is even accredited in the court of the Low King.
Being diamond prevents him from telling lies, a seemingly fatal disadvantage in his profession, but he's apparently clever enough to overcome even this. He is so reliably honest that he is trusted to represent both parties in the partnership of Harry King and Dick Simnel.