“People ask me why I named all six of my sons George Foreman,” says George Foreman. “Well, when you’ve been punched in the head by Muhammad Ali, Joe Frazier, Evander Holyfield, Ken Norton – try see how many names you remember!”

The audience roars. We’re at the Emirates Stadium. Foreman is being interviewed by Sky Sports pundit Johnny Nelson, the final act of an evening organised by Simply Prestige Events that has seen live music, auctioning of sporting memorabilia and the boxer posing for a photograph with every person in the room.

The photographs were quite something. He sat in front of a camera, bald and besuited, as one by one a line of grizzled businessmen enjoyed their five seconds in ‘George’s grotto’. He beamed at each new arrival before striking some variation of the clenched fist pose. He never spoke, and after every flash he glanced at the computer monitor to check the latest photo. The number of similar George Foreman images around the world – raised fist, big grin – must run into the hundreds of thousands.

Exactly 41 years and 364 days earlier, in Kinshasa, Zaire (now the Democratic Republic of Congo), a 25-year-old George Foreman climbs into a boxing ring. He is the unbeaten and undisputed heavyweight champion of the world. Thirty-seven of his 40 victories have come within the distance. Across the ring, former champion Muhammed Ali performs the familiar shuffle. Many watching around the world fear for Ali’s life. As the referee calls the fighters together, the older man taunts the young champion. Foreman is unmoved.

In barely half an hour Foreman will have lost his unbeaten record, his aura and his title – and the Rumble in the Jungle will be on its way to being enshrined as the most famous event in sporting history.

Foreman has only one regret about that night. “I wish I’d gone across the ring and said, ‘good fight, champ’. I wish I’d done that.”

The transformation of George Foreman is perhaps the most definitive rebuttal to F Scott Fitzgerald’s maxim of there being no second acts in American lives. (In fairness to Scott, even he didn’t believe it.) The vanquished titan reborn as a genial preacher, and then the beaming face of the most famous grill on the planet. Salesman and statesmen, Big George went from Attila the Hun to Santa Claus.

After the boxing match I’d get up in the night… I’d keep jumping up trying to beat the count.

It’s surreal, shaking the hand that pounded the jaw of Joe Frazier, staring into eyes that once stared into Ali’s across the Zaire night. In truth, it’s hard to reconcile this George Foreman with that George Foreman. No matter how ravaged by their years in and out of the ring, Frazier and Ali remained unmistakably Frazier and Ali. Foreman, in contrast, bears no obvious ill-effects from his boxing career yet is unrecognisable from his youthful prime. Perhaps it’s the decade of happy gluttony that swelled his frame to beachball proportions. Perhaps it’s the lack of hair. Perhaps he just smiles more.

Today’s Foreman has much to smile about. The endorsement of the Lean Mean Fat Reducing Grilling Machine has helped earn the father-of-12 a fortune that’s estimated at $250m. (By way of contrast, Muhammed Ali sold the rights to his name and image for $50m in 2006; Joe Frazier spent his final years living above his Philadelphia gym.) Whatever the reason for Foreman’s trip to north London, he certainly isn’t doing it for the money.

The man loves an audience: his voice is beautiful, a Texan baritone capable of both comedic patter and majestic invocation. The gag about his sons is delivered with the glee of the funnyman who knows he’s guaranteed a laugh. Yet when he recounts how “I was dead and alive again”, the elongated flatness of that “de-ad” takes you down into the depths.

But we run ahead of ourselves.

George Edward Foreman was born in Houston, Texas on 10 January, 1949. Raised by his mother in Houston’s Fifth Ward (known as ‘the bloody fifth’) – child number five of seven – his prospects seemed bleak to non-existent.

A promising footballer in junior high, his frequent truancy and eventual dropout scuppered any hope of emulating his childhood hero, Cleveland Browns fullback Jim Brown. A self-described “teenage thug” with “no chances at all”, Foreman and some friends signed up for Lyndon Johnson’s 1964 Job Corps programme and relocated to California. There, Foreman was introduced to boxing by future coach Doc Broadus as a means to control the violent temper that nearly saw him expelled from the programme.

After a brief, ill-fated return to Houston, in which the unemployed 18-year old threatened to return to his old delinquency, Foreman returned to California, boxing and to Doc. A successful amateur career culminated in triumph at the 1968 Olympics, with Foreman winning the USA’s second consecutive heavyweight gold medal after Joe Frazier in 1964. (Cassius Clay claimed light heavyweight gold in 1960.)

Today Foreman counts the gold medal as his greatest moment in boxing.

“Let me tell you, there has been nothing that comes close to the feeling I had as a 19-year-old boy who’d never had a dream come true. That was spectacular.”

“You sit there on the medal platform, with the national anthem in the background, and you kept thinking, ‘I’m going to wake up in a minute. This is a dream.’ Then the day after you wake, you say, ‘I'm going to wake up the next day. This is a dream.’ It haunted me for days because I thought I was dreaming.”

Better than his two championships?

“I was happy to become heavyweight champion of the world, a tremendous after-feeling. Then, winning that title again in ’94, it was like, ‘It’s impossible! It’s gotta be impossible!’ Those are the feelings I had. But to say one was better than the other – I couldn’t. Only the Olympic gold medal was distinctive.”

He demolished Frazier in Jamaica, flooring the unbeaten champion six times over two brutal rounds. If that night marked the birth of the Foreman legend, the 1974 knockout of Ken Norton, also within two rounds, proved a career highpoint. He bestrode the heavyweight division, colossal in body and mystique.

Foreman drew his aloof persona from former stablemate Sonny Liston. “I saw the way that Sonny Liston feared people, and how he’d look you in the eye, didn’t say much. I thought ‘mean will get you to be champion, I'm going to be meaner than him.’”

Was he happy during this period?

“I was just imitating someone. That was his life. No-one enjoys living someone else's life.”

And then came Zaire, the decision to grant an ageing has-been a final payday, and the inadvertent tumble into cultural mythology that began the moment Ali’s right glove slammed onto Foreman’s jaw with 13 seconds remaining of the eighth round. Twenty-two months after gestation, the ogre was slain.

Foreman admits “I lost the fight fair and square”, the furious pursuit of a decisive punch draining away all of his stamina as Ali absorbed his blows against the ropes.

“I remember in about the sixth round, I realised, ‘man, someone lied. This guy’s tough!’ And he whispered in my ear, ‘is that all you got, George?’ And I can sincerely tell you now, that was all I had.” He chuckles.

“I really should have been more prepared, and my corner people should have been prepared to tell me how to win. But that’s not gonna be through the knocking out of Muhammed Ali. If I had to do it all over again, I still wouldn’t have knocked him out!”

The celebrated 1996 documentary of the fight, When We Were Kings, won an Oscar but largely reduced Foreman to the role of hulking antagonist matched against Ali’s dazzling heroism. Foreman is phlegmatic.

“Every time when I watch it, I keep thinking, ‘I’m gonna win now!’ And I keep thinking every time, ‘I’m gonna get him now, this time I definitely got him!’ And I keep on losing, so I just stopped watching it.”

Did he realise the enormity of the event at the time? Comprehend his place in history?

“I really didn’t because I was so much a part of it. After it’s all over, and you start trying to make a comeback, and people are saying, ‘what happened to the fight?’ – then you realise, this was a major event that I was involved in. Not while it was happening, only years after, maybe ten years after.”

He departed Zaire a broken man. The defeat would quite literally haunt his dreams. “After the boxing match I’d get up in the night… I’d keep jumping up trying to beat the count. This went on for a couple of years. I couldn’t outlive that moment. So you keep saying to yourself, ‘If! If! If!’”

Gripped by depression and desperation, Foreman even resorted to fighting five men in a single night in a vain attempt to recapture his lost aura. Watching on from the ringside, Ali merrily goaded his former foe.

It was an attempt to prove his questioned stamina that led to his second defeat, on points to Jimmy Young in 1977. “I went 12 rounds intentionally,” insists Foreman. “I was trying to prove to the world I could go 12 rounds.”

Ironically, it was in the 12th round that Young inflicted the second knockdown of Foreman’s career. Although Foreman got up and believes he won the fight, the judges disagreed and awarded Young the decision.

Yet it was not the defeat but the immediate aftermath that changed Foreman’s life forever. In the changing room, Foreman collapsed.

“I went back to cool off in the dressing room and in a split second I was dead and alive again, I was in the room screaming ‘Jesus Christ has come alive in me!’ They rushed me to intensive care and I stayed in the hospital a couple of days, and I tried to rationalise what had happened to me. I saw blood on my hands and my forehead, I saw screaming…”

Foreman’s trainer Gil Clancy assumed the extreme heat of the Puerto Rican night, coupled with the exertions of the ring, had triggered some form of hallucination. Foreman is convinced he found God. Whether due to dehydration or the divine, the episode prompted Foreman to retire immediately from boxing. “For ten years I couldn’t make a fist. I couldn't box, I couldn't go back into the gym.”

Instead the former terror of the heavyweight division fully embraced a life of anonymity and the church. He shaved his head, feasted on burgers and spread God’s word to people on street corners. It was the happiest decade of Foreman’s life.

I wish I had enjoyed my journey a bit more. I was on edge

“There are two doors in life. One is the big high-side where you’re a celebrity and you go in the front door and everything is big. Then there’s the backdoor. You still come in and there isn’t any celebrity. You’re not a celebrity, you’re just a regular guy, and I learnt to love that. People liked me for who I was.”

“I was ordained an evangelist and started working, preaching on the street corners, telling everybody about my experience. I was 300lbs, I cut my moustache and my hair – nobody even recognised me! I could be myself. Go to the grocery stores and look at bargains… I just loved it.”

Once he began officiating weddings and funerals, ‘Brother George’ appeared to have left his former life behind for good. “I never intended to box again! But then that phenomenon occurred – I became broke.”

And so, age 38, the now-even-bigger Foreman strapped on the gloves. Also older, wiser,

and infinitely more affable, his was the type of comeback so beloved by America. With Mike Tyson occupying Foreman’s old role as boxing’s bogeyman, George swiftly became the nation’s favourite uncle.

Through a combination of ring savvy and undiminished power, Foreman boxed his way to two world title shots in 1991 and 1993. He was outmanoeuvred by his younger opponents and lost both on points. 1994 brought a third title fight, against new champion Michael Moorer. The memory of those two previous defeats dictated a strategy of patience.

“I realised if I knocked him down once in the first round or second round, he would get up and be afraid and outrun me, and they would give him the victory on points. I knew that!” His voice is emphatic. “I knew I had to drop him, and it had to be for good.”

In the tenth round, Foreman landed a straight right, “the best one I ever delivered in a boxing match”, and Moorer crumpled to the canvas. The 45-year-old champion, the oldest heavyweight title winner in boxing history, dropped to his knees in gratitude.

“I never took religion into the ring, never pointed up to the sky… But I remember in my hotel room, I prayed. I said, ‘God, I never bring this up but if I win this time I’m gonna get on my knees and say, ‘thank you, Jesus!’’ And after it happened, I got down on my knees. This time it was all real.”

Another remarkable night in a remarkable life. Yet if Foreman could relive one of his many triumphs, it wouldn’t be that moment of catharsis, nor the epochal destruction of Frazier, nor even his beloved Olympic gold. Instead Foreman nominates “this fight in Seattle, Washington. A guy named Carroll.” [His fifth professional contest against Johnny Carroll. Foreman was 20 years old.]

“He stared me down in the face like he was a snorting bull. He hadn’t seen me fight…he thought he was tough. The bell rang and he came out at me, and when I threw I missed him. I missed him by a foot! But he felt the wind – and I remember him holding me thinking, ‘My God, somebody lied!’ Then I tried to get him again, and this time I missed him by maybe six inches. And I was upset then, so this time I said, ‘I’m gonna knock him out’, and I threw with all my power, and I missed him by an inch – and when I did he just fell. I didn’t touch him but he fell. The whole crowd saw him fall without being hit! I told him to get up, the crowd told him to get up, they threw candy wrappers, and he didn’t get up. And I stood over him so sad because they could see what he had done.

“Afterwards, he came to me and he said, ‘George, you really wanted me to get up, didn’t you?’ I said, ‘yep.’ He said, ‘you wanted to kill me, didn’t you?’ I said, “yep.” He said, ‘that’s why I didn't get up.’ I thought, ‘that makes sense’, and I laughed. I’ll never forgot that.”

It’s a good anecdote, capturing the fearsome Foreman of lore, and also the young man beneath the monster mask. By beating Frazier, Foreman was thrust into the global spotlight 12 days after his 24th birthday. Older heads have been turned by lesser celebrity.

On the subject of regret, he is poignant.

“I wish I had enjoyed my journey a bit more. I was on edge. I was mean. I went to Kingston to fight Joe Frazier: I never even saw one inch of water, the colour of the sea in Jamaica! I was so focused on the boxing match, I didn’t see anything, I didn’t even listen to the local music. After the fight was over, I got on the plane and didn’t look back.

“I wish I had enjoyed my journey. If I could do it all again, I would have told myself: “man, this could be the journey of your life. Enjoy the food, the flavours, the curry…”

One can’t help but note the timing: his last days of relative anonymity. The Olympic gold soon to be superseded by the championship belt; the nights of shocking the likes of Jonny Carroll long since past. For many years after Kingston, nobody would like George Foreman purely because of who he was.

Yet today he is revered. At the Emirates, the interview concludes and the room surges forward for a final photograph with the two-time world champion. He beams and glad-hands, the last of the great heavyweights, a living monument to a golden age.

Foreman nearly returned to boxing aged 55 until his wife intervened. “She said, ‘George. Isn’t that the way you want to leave the sport? Feeling like you could still do it?’ And I never said a word about a comeback again.”

So does the prospect of just one last hurrah ever enter into his mind?

“All the time!” He chuckles. “But my wife was right: I left the sport feeling like I could still do it. Most guys leave it on the floor, all beat up and everything. If I was to make a comeback now, it would be against a lightweight, that’s for sure!”

George Foreman was at the Emirates with Simply Prestige Events: simplyprestigeevents.com