I had a bet and backed for a win SYW into Flow place, Gresham place.
I watched the betting for a while on Sat Morning for SYW and in one move it went from 1.80 to 2.1 with no move for any other horse that I could reckon. I then cursed myself as I know from experience that that move suggested that it was known that SYW could not win later in the Day.
The Bookies aren't God and information comes from stables(Trainers, insiders etc) about any horses chances. imo
On Sat morning at a certain time with the blow from 1.8 to 2.1 the knock (definite) for the horse was possibly known. imo only Md