The Undertaker has revealed all over his injury hell, crippling doubts over his ability as he gets older and his biggest fears in a stunning tell-all documentary.

The WWE legend – real name Mark Calaway – has had film crews follow him for the past three-years to chart the highs and lows of one of wrestling’s biggest icons.

The five-episode doc – which starts on Sunday after the Money in the Bank pay-per-view on the WWE Network – gives fans a behind-the-scenes look at one of the industry’s biggest kept secrets.

The 55-year-old is known for never breaking character in public, and has remained a mystery for 30 years as he led Vince McMahon’s company to roaring success.

But incredible footage captures Taker at his most vulnerable, nearly breaking down in tears at times as he battles to keep his body and mind in shape.

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Taker tells of being in constant pain, his numerous injuries and surgeries, just to get back in the ring and entertain his adoring fan base.

He charts his iconic WrestleMania streak, which ended in defeat to Brock Lesnar in 2014, taking his record to a staggering 21-1.

And the now family man reveals his biggest fears, how he was inches from death and why he will only go out on HIS terms.

Taker says in the opening of the first episode over his brush with death following an incident during a match – but won’t be told when he should retire.

He said: “I want them thinking, ‘this guy’s got a lot left in the tank’.

“If I can leave with that, I’ll be content, I can walk away. I say that, but I’ve been saying that for a long time.

“You start to hear things, people talking, ‘he’s too old, he shouldn’t do this, he shouldn’t do that’. That’s up for me to decide.

“For the last few years, I’ve had this internal struggle, I don’t want to stay too long.

“Every time I think I’m out, they pull me back in. You’re about to put your whole legacy on the line.

“You start second guessing yourself, ‘is it me? Have I lost that big a step? Are you the reason why this stuff is happening?’

“I was two inches from making my wife a widow, my kids fatherless.

“I’m either going to go out in a match that’s fitting for the Undertaker at WrestleMania, or I’m going out on my shield, one way or another.”

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The Undertaker had no idea of his now well-known incredible success at WrestleMania until it was brought to his attention.

He went on to be undefeated for 21 matches before the loss to Lesnar, and is currently at a record of 25 wins and two losses.

Calaway said: “It just happened man, someone brought it to me attention.

“Someone said ‘You know you’re undefeated at WrestleMania? Am I really? That’s cool.

“The streak is the only thing that made it OK for me to work once a year. I had to defend the streak.

“It takes its toll. I had a five-year stretch where my schedule would be prepare for Mania.

“I would have my Mania match, then have some kind of surgery to repair whatever had been bothering me going into that match.

“I’d go straight from rehab right into training to be ready for Mania again.”

The Undertaker also told of his crippling doubts before his matches at Mania, leaving him a bag of nerves before his ring entrance.

He said: “The process has become bigger and bigger each year to get me to a place where I can go out and deliver that performance.

“If you stay around as long as I have, your body is going to break down at some point.

“My body was at the limit of what it could take.

“I can tell you for certain after all these years and all these WrestleMania’s there’s not one time that I’ve not been extremely nervous or had that feeling in my stomach before I go out.

“It is hard to even describe all the emotions you go through, the jitters, the concerns, it’s big time.

“I used to be a tough son of a bitch. What happened?

“It’s a huge challenge trying to work once a year and have your timing, cardio, your gimmick.

“It’s tough, but it’s my reality, that’s where I’m at, at this point in my career, I can’t work a full schedule, there I said it.

“I love and respect this business so much, and all I ever wanted to be was a wrestler.

“Would I have imagine the success of that character and longevity? There’s no way.”

He also revealed his biggest fear is fans having to tell their children that he is past it and can no longer compete with the younger wrestlers.

He added: “Regardless of my injuries, regardless of my age, regardless of everything that’s happened.

“If I’m on the card, there’s some young guy, who is making a lot of the shows throughout the year who may not be on the card.

“It’s my duty to make sure that it’s worth putting me on the card.

“Nobody would probably say anything to my face if I stunk it up, but I would know and that’s one of my biggest fears, is become a parody of myself.

“It would kill me to know, some dad, who watched me when he was young, has to turn to his son and say ‘man, he’s moving kinda slow now, but you should have seen him 10, 15-years ago.

“I know reality is I’ve slowed down, but still I try to bring the best package that I can on that night.”

The episode ends following his ‘retirement’ match against Roman Reigns at WrestleMania 33 in Orlando, Florida … but is really the end for the Phenom?

This story originally appeared on The Sun and is reproduced with permission