LAS VEGAS (AFP) — In a black-walled gym tucked away in a quiet corner of Las Vegas, Mike Tyson looks on approvingly as the unmistakable sound of violent, powerful punches fills the air.

Thirty-seven years after rewriting boxing's record books by becoming the youngest heavyweight champion in history at the age of 20, Tyson is plotting another ambush.

The 57-year-old has been hired to help train mixed martial arts star Francis Ngannou ahead of the Cameroonian fighter's money-spinning heavyweight boxing showdown with Britain's Tyson Fury taking place in Saudi Arabia on 28 October.

In the eyes of bookmakers at least, the odds are stacked against Ngannou, who will climb into the ring against the undefeated Fury next month having never boxed professionally. Ladbrokes have installed Fury as a 1/10 favorite; Ngannou a 6/1 underdog.

Yet as the 6ft 4in (1.93m), 264lb (120kg) Ngannou unleashes an array of punches on his heavily padded trainer, Dewey Cooper, the mood is anything but pessimistic.

Occasionally, Tyson, standing to one side, will intervene to correct a movement or suggest a subtle tweak. Ngannou, a long-time fan of the American boxing icon, relishes each suggestion.

"He comes from time to time to lend a hand, to give his expertise," Ngannou told a group of reporters during a workout.

"I had specifically asked for him to train me four years ago, long before this fight was announced, the first time I met him."

"He has something inspiring, something motivating. If I could ever have just a tiny piece of what he has, boxing would be very easy for me."

Ngannou, 37, has taken a long and unconventional road to his boxing debut.

He first took up boxing in his 20s in his native Cameroon, later moving to Paris hoping to forge a professional career.