Tyson Fury revealed he broke three of his father's ribs at the age of 14.
The Gypsy King, 33, released his autobiography 'Behind the Mask' in 2019 with some fascinating insight into his life growing up as a child.
Fury was born two months premature and weighed just 1lbs, but his father saw the fighting spirit in his newborn baby, and named him after boxing legend Mike Tyson as a tribute to the former heavyweight champion of the world.
But even Big John was caught by surprise when his oldest son cracked his ribs during a sparring session which meant he was forced to take a bit of a breather.
Fury wrote: "My dad did get up an up-close-and-personal view of my talent when I was just fourteen.
"He was still keeping in decent shape and was working out on a bag in our shed and we got talking about his career.
"I cheekily said to him that I'd been watching him on video and he wasn't that good!
"So he said, 'Right let's get the gloves and see how you can handle yourself.'"
"He thought he was going to give me a right beating but early on I cracked him with a left hook.
"Boom! His ribs cracked but he came right back at me.
"But I was beating him up and we agreed that it was better for him to sit down because I was getting the better of him.
"In the fourteen fights he had as a professional he admitted to me that he had never been hurt like that before.
"i think we both knew then that I was a bit different and that making a career for myself in professional boxing was not going to be a problem for me - at least in the ring."
Standing at 6ft 3in, Fury Sr fought 14 times as a pro boxer in the 1980s and 90s, compiling a record of 8-4-1 at heavyweight.
John, who later coached Tyson and his brother, Love Island star Tommy Fury, still remembers the exact moment their lives changed forever.
Speaking to talkSPORT, he said: “At 14 he was around 6ft 5in tall and weighed 16 stone.
“He was a big fat kid, not really lean because he loved a burger.
“A friend of mine said way back then that, although he had layers of fat on him, he had never seen anyone move like him and that he could be a champion.
“And you know what, what’s in a man, you can never take out.”
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