ITV1’s Ninja Warrior UK show decided to ramp up the difficulty from the heats, meaning few of the contestants managed to finish the course.
Even Sébastien Foucan – legendary French parkour originator and star of Bond film Casino Royale – failed to complete the course, coming a cropper in the rolling log penultimate section.
But Hay stormed to the end, finishing with a punishing rope climb to hit the button and stop the clock at three minutes and three seconds.
The next fastest competitior was Owen “The Stuff” McKenzie with 3.38 – 35 seconds behind the “Bearded Ninja” Ali, who is the only Scot left in the competition.
And Hay told us he could probably have done it quicker “if I wasn’t buggering about so much.”
He said: “It was definitely the hardest course ever, which is shown by how few finished.
“I did kind of take my time though, as I didn’t want to make any daft mistakes.”
What’s more, he told presenter Chris Kamara that he hadn’t had a wink’s sleep the previous evening, and that he felt “rubbish” both the day before the semi-final, and the day after.
But he added: “As soon as I was on the stage, I immediately felt better. The crowd is awesome.”
Over the two semi-finals, only 10 athletes actually completed the course, the other 50 finalists being graded on where they reached.
Ali said: “If I knew I was going so fast, I’d probably have slowed it down a bit.
Looking ahead to the first stage of the final which airs this Saturday, May 26 at 6.30pm, Ali said: “My fast time meant I had to wait until last in the final, which certainly piled on the pressure. The first stage of the final is a knock-out competition.
“There are no second chances in this one.”