Willbury identifies this guy as the head patent officer at the Patent Hall (14.68). Further, he says: "'He knows me from a certain legal case. And if I let one or two things drop in conversation with his receptionist, I think he will see me very quickly'" (14.72). Seems like Mr. Trout may not have always conducted himself in accordance with Willbury's strong ethical sense. This is confirmed when we find out he's behind the theft of Marjorie's invention, and its nefarious repurposing as part of Snatcher's grand plan.
He gets his just desserts, though, when some trotting badgers tear him up and, as a result, he's "bandaged from waist to knee" (28.48). In addition to the injuries, Louis and his son get tricked into stepping into the resizing machine by Snatcher, who shrinks them in order to funnel some more size into Framley. Too bad for them.