A phrase referring to a horse that led all the way and went on to a run-away victory.
Along the course of a racecourse, there are a number of posts, usually placed every two-hundred metres.
They typically indicate how long is left to run to the winning post.
By making every post a winner, the horse races as if every one of these distance markers is the winning post. In other words, racing at the head of the pack for the whole race.
"Typical Gai horse, made every post a winner. Never in doubt."
