Head on view - Bookies goffer or Boys in the van?

"They" instantly know every photo where there is likely to be a stewards called,and bet accordingly.
Sure it's often obvious to everyone the leaders have bumped,or one has moved across from the TV pics,but at other times it's only the head on view that shows any riding offence.I suppose it's the usual guideline if it seems too good to be true It usually is - well in photo odds anyway!