The 30 seconds that shook Fury and took Usyk to the summit of boxing | Barney Ronay

Either side Usyk subjected Fury to a horribly draining expression of his own fighting personality, pushing him around the ring, throwing punches from every angle (at one point he seemed intent on battering Fury in the chest) and never allowing his own unblinking stare to leave Fury's field of vision.

Fury showboated pointlessly at times. At others he simply turned his head away and walked across the ring, giving himself a moment of reset. It has been said that simply sitting across the table from the chess grandmaster Garry Kasparov was utterly exhausting. Facing Usyk must be just as gruelling, with the need to be always on, always tensed, always facing down that weather front of pressure.

Then there were those 30 seconds. It began with Usyk landing a sudden raging left to the side of Fury's head. Fury's face changed. He knew. He leaned back on the ropes, feeling for his legs. Usyk pressed the gas, threw three more lefts to the side of the head, as Fury went windmilling back across the width of the ring in search of solid ground.

The key to those exchanges was watching the feet of both men, Usyk snapping his toes together, clicking his heels, balance perfect even with the kill-moment adrenaline pumping; Fury loping about like a drunken camel, somehow staying upright, dipping and bobbing like a doomed fighter plane still dodging flak.

Fury touched all four ropes in the space of 20 seconds as he fled that stinging, smothering presence. He ended up collapsed in Usyk's corner. The ropes held him up. The bell saved him. The referee, Mark Nelson, really could have stopped the fight at that point rather than simply awarding a knockdown. Had this not been Fury, the resurrection man, and also the larger man, perhaps he would have done.

From there it was a tribute to Fury's extraordinary fighter's heart that he took it to the end, that he came back to fight three more rounds, and that he ended the night on his feet. Perhaps that will be enough to persuade him to trigger the rematch clause. On the other hand Fury is 35 now, with a lifetime of scar tissue, worn down not just by all those heavyweight rounds but by the constant war with his own body and mental state.

The years have been hard. Having a great chin is a vital quality. Having a great chin also means you get hit a lot. Coming back from depression and booze, gaining and then losing 10st (the equivalent of losing an entire adult Lionel Messi) are evidence of his will.

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But these things all take a bite out of you. Fury made an estimated £80m in Riyadh's Ring of Fire. It would be most sensible to retire now. But then, what has sensible ever had to do with it?

The Kingdom Arena had been a familiarly glossy spectacle as the fighters walked out, peopled, we were told, by a galaxy of stars, although this seemed to consist mainly of regime favourites. Most notably Cristiano Ronaldo was ringside, smooth and primped and glazed with plasticised good health, ideal frontman for global sport's new reality as the plaything of a propagandist dictatorship.

Usyk entered the ring looking brutally focused in a feathered fur hat and traditional dress. Fury arrived in a shirtless waistcoat and rakish black cowboy hat, like a strippergram version of the Edge from U2. He dad-danced to Barry White and Bonnie Tyler. He gurned across the ring as Usyk simply stared.

From the start Usyk stamped on the gas as Fury weaved and ducked close to the ropes. Muhammad Ali floated like a butterfly. Fury floats like a shipping container on a pair of roller-skates. But his slippery speed kept him out of trouble as Usyk found his range, feet constantly shuffling, back fat wobbling over his colossal green shorts.

There were some solid Fury uppercuts in the second quarter of the fight. But otherwise this was a reeling-in, the angles of attack so sudden and varied Fury never quite seemed able to unload and assert his own physical advantages.

Usyk sank to his knees after the decision and shouted "Slava Ukraine!" Fury has always drawn strength from his own outsider identity, a visitor from the fighting fringes, Grendel in baggy shorts, although it remains open to debate what added value there was in his dad leaning over SugarHill Steward's shoulder and shouting "We're fighting men!" in between rounds.

But Usyk's own outsider story is a modern sporting marvel. He was born into communism in the Soviet Union. His home town has now been bloodily re-subsumed by Vladimir Putin. The same weekend Usyk was fighting in Riyadh Ukraine was launching a massive, all-or-nothing drone attack, the front line stretched thin. As Wladimir Klitschko has pointed out, watching Usyk provides an hour of respite from bullets, bombs and missiles.

Carrying this weight, Usyk now stands as the greatest boxer of the modern age. The champion is 37. This could just as easily be the end for him too. Most likely there will be a rematch, if only because money will demand it. But Usyk really has nothing left to achieve from here, no more doors left to unlock.