That article mentions Barney Curley, I'd recommend his book giving a little back. In it he documents a coup he pulled off against the bookies on a horse running

That article mentions Barney Curley, I'd recommend his book giving a little back. In it he documents a coup he pulled off against the bookies on a horse running at a small English course Cartmel in the 70s iirc. The key point was that there was just one telephone at the course. Most bets are settled at SP which is the on-course starting price. If the big chains are getting a lot of money on a horse they'll get their agents to put money on that horse at the course to bring the price down and reduce their liability. On that day Curley's people put a fortune of money on before they bookies realised there was something up. They hid it by betting in doubles where there's less scrutiny but then they pulled the other horses out of races which had the effect of converting those bets into singles. The routine would be for the on-course agent to phone head office to see what they had to do. On that day, Curley had a burly crony hogging the phonebox as he tried to keep up with the health of his aunt who'd been taken ill. No one was able to shift him until the race went off.