He recounts how he fell four steps from the bottom in pitch darkness and landed on his left knee, which was impaled on a bolt sticking out of the floor, causing excruciating pain.
Despite this, he managed to finish the drill, but found that his knee wasn't working properly when he jumped off the boat's helipad into the water at the end of the exercise.
Paramedics were called when Prince William, who was present at the time, saw the extent of Harry's injury and turned pale.
His knee was bleeding profusely and the Palace announced weeks later that his Army entry would be postponed indefinitely.
This reveals the reality of the challenges and risks that military personnel face, even during training exercises, and the sacrifices they make for their country.
