Former undisputed heavyweight champion Mike Tyson has revealed a childhood molestation turned him into a fighting machine.

The Hangover star was talking about his challenging childhood in Brooklyn, New York during an ESPN E:60 interview with old pal Jeremy Schapp when he let slip he had been the victim of a local pervert who dragged him into a building and “molested” him.

Tyson immediately tried to change the subject but Schapp persisted, revealing that in all their pre and post-fight chats over the years, the fighter had never opened up about the drama.

“It was nobody’s business to know,” Tyson said, becoming defensive. “It doesn’t make me any less of a man, because it happened. It’s just something that happened, not a big impact in my life.”

But the former champion then told Schapp the molestation experience, combined with the factor of childhood bullies and the gangs that ruled his neighbourhood, inspired Tyson to toughen up, develop a thick skin and hit the gym.

The unusually candid star had to stop the interview with the sports reporter at one point as he teared up while recalling his late mentor Cus D’Amato, who took charge of Tyson’s boxing career when the sportsman was a teenager.

Tyson competed in the ring from 1985 to 2005. He reigned as the undisputed world heavyweight champion and holds the record as the youngest boxer to win a heavyweight title at 20 years, 4 months and 22 days old. Tyson won his first 19 professional fights by knockout, 12 of them in the first round.

On June 11, 2005, Tyson took part in the final bout of his career when he was stopped in the seventh round by journeyman Kevin McBride. After losing three of his last four fights, Tyson announced his retirement from boxing because he felt he had lost his passion for the sport.