Head to head betting - potentially the greatest betting rort since the Romans' prisoners played the lions.
And racing's integrity unit says it can do nothing to stop it or possibly even police it.
The TAB recently introduced head to head betting, pitting two horses and/or two jockeys against eachother in selected races. Seems innocent enough - except that if jockeys decide to take advantage of it, it will become the easiest punting opportunity of all time to rort.
Here's how it could work: Lester Piggott, riding Sunline, could say to Malcolm Johnston, rider of Bonecrusher, the other head to head horse, "Hey, Malcolm, Bonecrusher races back and I'm going to lead. Head straight to the rail behind the field from your wide draw and be unlucky enough to make sure you don't beat me home.
You might say that comes under the Rule of Racing that covers giving a horse the opportunity to fill the best possible finishing position.
Two things here - you wouldn't be doing it in a race that contained a Bonecrusher or a Sunline, it would be two lesser known horses whose racing habits are less obvious. Therefore it would be easier for one head to head jockey to disguise his or her actions.
And here's the rub - there is no obligation on a rider to press a horse to do better if it is clear that horse is about to finish outside the dividend or stakemoney placings, meaning those further back than sixth.
Which means if the jockey on a horse on which head to head betting has been taken is running seventh at the 200m and the other head to head horse is in the first six ahead, the rider running seventh is not obliged under the Rules of Racing to pursue the other horse.
In fact, using excessive force, or a strong level of force, on a horse outside the first six, unless finishing strongly, will lead to a severe warning.
It means racing stewards have no means of protecting the punters on the horse running seventh.
If both horses nominated in the head to head are back in the field there is no obligation on either jockey to do anything. They can decide which finishes in front of the other.
It is understood the Racing Integrity Unit recently discussed the subject and decided the Rules of Racing do not permit the opportunity to change or to take action.
The head to head jockeys' bet in individual races, entirely separate from the Jockeys' Challenge which incorporates all races on the day, is another potential avenue for danger.