Okay, so it was a long shot. Never in a million years would this guy call him out for using a coloured ink on his homework, but that had been the only thing he could think of that wasn't personal. That only really left one thing, and Bro hit it right on the head. Arthur started slightly, then rubbed one hand around the back of his neck before clasping both of them in his lap.

"I got the distinct impression I'd overstepped my boundaries." He lifted one thick eyebrow slightly. "Until now I hadn't been given any reason to suspect I was wrong."