So it's no surprise the contestants struggled, and needed to find their own ways to cope with the tough experience.
Here Locky aka Rudimental's DJ Locksmith and former boxer Tony Bellew reveal what got them through, and the tough moments along the way...
You're both athletic men, did that help you with Celeb SAS?
Tony: I’ve trained all my life but nothing prepares you for that. When you look back, physically it’s not that much work you’re doing, but it's the effect of the sleep deprivation and lack of food, plus little things winding you up like being in wet clothes constantly and those horrible boots. The fittest man in the world would have struggled in there, it’s about mental strength, you’re on edge the whole time.
Locky: I agree, you can do as much training as you want but it will never prepare you for what you’re about to endure. I did quite a bit of training, carrying things, long walks and hikes, but you’re being mentally tested. You're living off very few calories a day, it feels like nothing.
Were you surprised by how tough it was?
Tony: The thing that shocked me the most was the beds. I was hoping and praying that when we got our heads down on that first night someone was going to come in and say, "Right guys, open your eyes, that’s it for the night, there’s a nice bed round the corner". But nothing like that happened! I was sleeping on this thing they called a bed with my feet hanging over the end of it, I had boots on, it was painful and stressful.
Locky: The final phase (featured in tonight's episode) was interrogation. We were blindfolded and I could only assume it was Ant who kept hitting me in the stomach. By this time I had completely lost it, my temper had gone - he was hitting me and I’m head butting him back.
What helped you push through the pain?
Locky: It was a sense of pride for me. Joey Essex was in the show with us and all I could see was the image of him in my head. There was no way I was leaving SAS while he was still there, no chance - my boys at home would never let me live that down!
The final of Celebrity SAS: Who Dares Wins airs tonight on C4 at 9pm. To find out what else is on telly, check out our TV Guide.