The parents of an army friend of mine used to run a pub/hotel in Gazely, Newmarket - you could see the tack from the windows. A group of us stayed there for a few days in the 70s and i overheard a group of young jockeys sat in the bar, deciding who was going to win the apprentice race the next day. I couldn't see them but i overheard one of them say, "If the rank outsider wins, it would look suspicious so we'll go for the next best price."
Yes, of course i backed the winner:-)
I suppose those young lads weren't paid a great deal and did this to supplement their income. I still steer clear of apprentice races whenever possible