It was Channel Nine's $15 million gamble that proved to be its greatest masterstroke as audiences switched on in droves to its Ninja Warrior series, much to the dismay of the network's rivals who have hit their own "warped wall".

"They must be kicking themselves over at Seven right now," crowed one television executive from Nine's Willoughby bunker this week.

PS can reveal Nine rivals Channel Seven and Channel Ten both cast their eyes over Ninja Warrior, though neither network seized on the format, which originated in Japan and became a huge hit in the United States, despite it being shopped around locally by production company Shine Endemol for several years before Channel Nine finally signed on the dotted line.

Even Nine was uncertain about its prospects. In a high-level meeting of executives on the eve of the show's debut various Nine bosses offered their predictions on how well Ninja Warrior would rate with just about everyone in the room predicting it would hopefully get to about 1 million viewers.