RIYADH (AFP) -- Francis Ngannou once toiled in a sand mine, scavenged for food to avoid starvation and slept rough in a car park, so facing former two-time world heavyweight champion Anthony Joshua on Friday, March 8, is just another stop on his epic rags-to-riches journey.

"I've had a lot of experience in life," the softly-spoken Cameroon-born fighter says with characteristic understatement.

"I've built my fighting spirit as high as anyone else."

Ngannou has crammed a lot into his 37 years.

The child of a single mother, he had to walk six miles to school and from the age of 10 he shoveled sand from open quarries, his meagre income helping to buy food and books.

"It was work meant for adults, but we didn't have any options," said Ngannou of his back-breaking labors which paid less then $2 a day.

"Sometimes I didn't have a pen or a notebook. Sometimes no shoes, my uniform was torn. I looked crappy.

"I didn't like my life, I felt like I missed my childhood."

In 2012, at the age of 26 and fired by dreams of becoming a professional boxer, Ngannou, now boasting a towering physique carved from his brutal work in the sand pits, made a break for Europe and a better life.

Crammed with others into the back of a pick-up truck, he crossed the unforgiving Sahara, travelled through Nigeria, Niger and Algeria before reaching Morocco.

Then, after half a dozen failed attempts, he finally made it over the Mediterranean to Spain where he was promptly jailed for two months for making an illegal crossing.

Completing a trip of around 5,000km, he took a train to Paris, lived in a car park before local boxing coach Didier Carmont found him a place to live and a gym in which to train.

Despite an early fascination with Mike Tyson, Ngannou graduated towards Mixed Martial Arts and in 2021 became the UFC world heavyweight champion.

'Lot of hell'

Many scoffed when he opted to make his boxing debut against world champion Tyson Fury in the so-called "Battle of the Baddest" in October last year.

The doubters were silenced, however, when Ngannou sent Fury to the canvas in the third round before losing only on a controversial split decision.

His reputation and bank balance soared. He was paid $10 million for his night's work, a windfall which has helped the once shoeless Cameroonian purchase a luxurious home in Las Vegas.

On Friday, he will return to Riyadh to face 34-year-old Joshua whose career could be fatally holed if he loses.

"Of course I can knock Joshua out," said Ngannou. "I believe if I land on anyone, I will knock them out. The question is how to land? That's the hardest thing."

Joshua, a former unified WBO, WBA and IBF heavyweight champion, comes into Friday's 10-round fight on the back of three successive wins.

Before that, however, he lost back-to-back fights with Oleksandr Usyk who will fight Fury for the undisputed heavyweight title in Saudi in May.

"This Friday it's going to go down, so I can't wait for the opportunity to show my skills and combat this person who thinks he can knock me out," Joshua said of Ngannou.

"I believe I can knock him out. Definitely. I would love to knock him out and make a statement."

"He has to be ready for the shots which are coming his way because I'm a man who will be standing in front of him, bringing him a lot of hell."