Prince Harry talks about his struggles in the British Army bootcamp back in 2006.

The Duke of Sussex, who served a decade in the military, talks about various types of pain he had to endure in order to survive.

He pens in ‘Spare’: “They used a variety of approaches. Physical duress, psychological intimidation—and humor? I remember one color sergeant pulling me aside. Mr. Wales, I was on guard one day at Windsor Castle, wearing my bearskin, and along came a boy who kicked gravel on my boots! And that boy…was YOU!”

Harry continues: “He was joking, but I wasn’t sure I should laugh, and I wasn’t sure it was true. I didn’t recognize him, and I certainly didn’t remember kicking gravel on any guardsmen. But if it was true, I apologized and hoped we could put it behind us.”