Rhys Darby says the hardest part of his Bear Grylls adventure was not the rappelling, the climbing or the Tyrolean traverse. It was the final canyon crossing in Utah, where the comedian dropped off a cliff, hung upside down and had to fight his way back up.

The 52-year-old is the latest celebrity to join Bear Grylls’ Fox revival, Bear Grylls Is Running Wild, and his episode is set to air Tuesday, June 2. Darby said he knew Grylls from working with him on a few occasions years ago in New Zealand, where he also hosted A Wild Night with Bear Grylls, Live on Stage in 2012, and said the chance to get back into the outdoors was an easy yes.

The episode takes the pair into the Canyonlands of Utah, where they rappel, climb out of canyons and cross by Tyrolean traverse before the final stunt. Darby said the last section was the one that caught him out. He said he had done similar outdoor and army-related activities as a young man in the New Zealand army, but this was different. He said he had never dropped over a rock face and hung suspended upside down before, and once he got to the other side he struggled to pull himself off the rope and back onto solid ground.

That was the point where the friction showed through. Darby said he was never one to be scared of heights, yet he also described apprehension and unease when he was told to go over the edge of the giant rock face. He said he focused on technique, did not look down and kept telling himself to trust the ropes, but he also admitted he was tired by the time the final challenge arrived. The result was a segment that sounds less like a clean stunt and more like a test that wore him down before it finished him.

He said the experience took him back to his younger days in uniform and left him feeling like a young soldier again. After the final traverse, he said Grylls spoke to him immediately and he was emotional. That leaves Tuesday’s broadcast as the moment viewers will see how the climb, the hanging drop and the helicopter airlift looked on screen, but Darby has already made clear which part of the adventure defined it: the last rope crossing, not the rescue at the end.