We always met, just after five every morning, in the cool darkness of downtown Houston. The drive to the gym would be quietly eerie, the silence broken only by the hiss of tyres speeding through deserted streets until, on the corner of Clay and Chenevert, the car turned sharply into a blackened parking lot. I felt a little shiver every time the headlamps flashed across the blunt words painted on the cream strips of corrugated tin: Main Boxing Gym - House Of Pain.

Once inside, Evander Holyfield would be calm and alert, perhaps even happy, as he slipped out of his fluffy, white robe and sat on a chair close to the edge of the ring. As his huge neck and shoulders were massaged in readiness for another day's training, I'd sit on the apron of blue canvas. Looking down at his bowed head, it was impossible to miss the small logo on the back of his T-shirt. It spelt out both the name of his lucrative line of sportswear and his raw philosophy as a professional fighter: Holyfield Warrior.

I could also see the scarred hole in his upper right ear where, in desperation, Mike Tyson had torn away that chunk of skin and sinew before spitting it to the floor. Even bitten and bleeding, Holyfield had fought relentlessly against Tyson, proving that he could not be discouraged by mere punches or snarling teeth. "Iron Mike`" was ruined, beaten again by a better man - and the more ferocious fighter.

In Houston, Holyfield had returned to familiar and more tranquil territory. We were less than three weeks from this weekend's world heavyweight title unification fight against Lennox Lewis. But Holyfield was used to the hushed waiting and hard training, for he had fought so many big and dangerous men before: Riddick Bowe three times, Tyson and Michael Moorer twice each, as well as George Foreman, Larry Holmes and Buster Douglas. Only Lewis is left, brandishing the WBC belt Holyfield needs to add to his WBA and IBF crowns and so become boxing's first undisputed heavyweight champion since 1992.

But Lewis carries more alarming credentials than just another championship bauble. Even Holyfield has to sometimes admit that Lewis is younger, taller, bigger, faster and more powerful. He knows that Lewis will outweigh him by almost three stone. Lewis is also much the fresher boxer, having avoided the ravaging wars which define the 36-year-old American's contrasting reputation for determination and fortitude. Holyfield has trudged to the well of courage so many times that it's hard to believe that, one night, his usually flowing and bucketing punches will not make a dry and empty clank as he finally scrapes the bottom. In the end, boxing gets everyone.

On my first morning, feeling like death, I asked Holyfield if he ever tired of boxing's harsh rituals. He was only a year younger than me, I mumbled, as if in warning that a similarly bloated physical shambles might suddenly unfold on his 37th birthday. How many more 4.30 a.m. wake-up calls could he stand, let alone ringing punches to the head? Holyfield smiled broadly.

"Hey," he said in his warm Southern drawl, "one thing I realise is this: if you wake up with a bad attitude, if you can't find joy, then you're in trouble. If you learn to appreciate what God gives you, then you're gonna get the full joy and happiness we all crave."

Once an ordinary cruiserweight, weighing 178 lb (12 st 10 lb), Holyfield has gradually added 40 lb of muscled bulk to his already colossal heart. In boxing's purest terms of desire and dedication, a comparatively small heavyweight like Holyfield towers over his contemporaries.

Ring magazine recently ranked him as the third-best heavyweight of all time - behind only Muhammad Ali and Joe Louis and ahead of Jack Johnson, Jack Dempsey, Rocky Marciano and the rest. Even if such lists are random exercises in entertainment rather than logic, it remains a faintly ludicrous assertion. Holyfield would not have beaten Larry Holmes, boxing's last conclusive heavyweight master, in his prime. When they did fight, in 1992, Holmes was 42 but he still used his beautiful jab and ringcraft to trouble Holyfield.

Yet, even without the sheer brilliance or terrifying power of boxing's legendary champions, Holyfield's claim to a place in the pantheon is unquestioned, and is made all the more moving by being based solely on the depth of his resolve and the strength of his mind. He is as brave and as spirited a fighter as boxing has seen.

Yet I sometimes fear for Evander Holyfield. I remember seeing him and his wife, Janice, in South Africa just days after the second Tyson fight in 1997. Janice, a doctor, suggested that, "boxing is what Evander does. And he has to do it until the Lord releases him to do something else. I get less worried as time goes on. Sure, people say he looks a much better fighter now, but what's happening is that God is anointing him." Tyson might feel abandoned, and Holyfield anointed, yet the damage may ultimately be the same.

When Holyfield completed his extensive skipping and exercise routine, it was 7.0 a.m. As he began the first of his three-minute rounds of shadow-boxing, the light leaking through a wire grate turned from grey to a softer yellow. Holyfield's breath, and the phlegm-ridden remnants of a recent flu, fell from him in rasping stutters as he worked from one side of the ring to the other, striking out at an imaginary Lewis. The sweat glistened like tears rolling down his face as he sang the hymn blasting from his sound system: Jesus, I Am Thirsty.

Don Turner, his gruff old trainer, gestured towards a 22-year-old heavyweight, "Irish" Tommy Martin, a comparative novice after 14 fights. Martin was big and keen but, as if on cue, the day's first ambulance sirens cut through the air outside. Houston, three hours after Holyfield, sounded like it had woken from a long night. But Martin was only starting his nightmare. Holyfield hit him with clubbing rights to the head and lefts to the body. "Stay close, 'Vander," Turner instructed him. He held on to the top rope while the ring shuddered. "Closer, closer," Turner repeated.

Holyfield burrowed into his bewildered opponent, pretending that he was Lewis. It was proof yet again that, to overcome Lewis's physical advantages, Holyfield will pour ceaseless pressure on the British fighter, fighting him on the inside. As the punches thud into him from awkward angles, Lewis will have to answer unsettling questions about his resolve and stamina. If he can match Holyfield's stark desire, Lewis will win.

But Holyfield claims to have seen all he needs to dishearten Lewis. In his fourth round of sparring, as if in celebration, Holyfield uncorked a sickening right uppercut. Martin's head rocked back and, with a wincing moan of sympathy, Turner signalled an end. As he towelled down the gleaming Holyfield head, Turner crooned, "Closer, closer".

Holyfield and I sat one last time on the edge of the ring. He shone with renewed certainty. "If I fight a patient fight and stick to that game plan," he stressed, "I'll whup him easy. See, a guy like Lewis, if you put pressure on him, he can't do nothing. He'll be overwhelmed by the sensation. He'll only bother me if he runs. That's why I broke Tyson's heart. Anyone who tries to have a war with me I'm gonna destroy. And, y'know, in all his interviews Lewis's saying how he's gonna prove himself against me. An' as soon as you got something to prove, you're gonna come out aggressive. That makes the fight a whole lot easier for me."

Holyfield is a remarkably accommodating man but, when it comes to fighting, he just can't help himself. His knowing smirk is at the core of his ruthless selfbelief. And, for all Lewis's considerable talent and power, he lacks Holyfield's instinctive and strange love of violent struggle.

"Lewis don't have my faith," Holyfield testified. "He don't have my experience. He don't have my wisdom. He'll see right there and then, as I take everything he throws at me, that there's something special about this guy. Slowly, he'll start to wonder, `What is it that this man has? Why can nothing shake him?'

"Same thing happened with Tyson. His spirit cracked. It was amazing. Tyson was supposed to be my toughest fight, but I came into the ring smiling, beaming the rapture, inside just goin' `sheeeeeeewwwwwww!' It took me all those years to reach that point, to love the moment of stepping into a dangerous place. To fight every round and enjoy it. To praise the Lord at the end, but to also say, `Hey, I got that sucker! Did ya see me hit him? Whap!' I got that attitude against Lewis, 'cos now they sayin' that this gonna be my hardest-ever fight! Don't look too hard to me."

I was one of the many who'd thought Holyfield would be badly hurt against Tyson. I was one of the many who thought that he should have given up boxing years ago, when he first lost to Riddick Bowe. But he came back and beat Bowe in one of boxing's great heavyweight contests, just as he came back from a heart-scare to comprehensively avenge his earlier defeat by Michael Moorer. Sometimes, it's hard not to believe in Evander Holyfield.

I turned back to him and asked: "Will you beat Lewis on points?" Holyfield's words were quick and sure.

"Oh no, I'll knock him out!"

"Early?" I said, unable to remember the last time Holyfield had made such a prediction.

"Well, anytime before 12 (rounds) is early."

I laughed, as Holyfield became more grave. "No, I'll knock him out in the third." And, uncurling his chilling fight-smirk once more, he began to murmur another gospel chorus: "He knows, He knows, He knows . . ."

One "He" rolled into another, until I was no longer sure if it was God or Lennox Lewis who knew Holyfield's latest truth. "They both know," Holyfield suddenly whispered, as if he had read my mind, "they both know."