This one was tricky. The original sketch for it looked terrible, 'cause I hadn't any photo reference for it. If I can find it I'll post it later. The photo reference is fun in and of itself–me in a fluffy bathrobe lying prone of a chaise in the backyard.
Anyway, the question of why Steve Brixton is in a bathrobe atop a moving train is best answered by reading the book, WHICH IS AVAILABLE NOW.
UPDATE: Due to popular demand (2 comments), here's my first attempt at a sketch, with no reference at all. I think this got approved, but I'd always promised to fix the dodgy drawing after shooting some photo reference.
Lacking a train and a 12-year-old boy, I put on my wife's robe (it actually has "Dr. Rex" stitched on the front–very hot) and lounged on a chaise.