Dillian Whyte's hopes of a world-title shot were wrecked as Alexander Povetkin twice rose from the canvas to land a knockout win that will stun boxing.
The Russian had been out-boxed for three rounds and was down twice in the fourth as Whyte mixed poise with power.
But just as it looked as if Whyte would close in on a shot at the WBC world heavyweight title, Povetkin produced a devastating uppercut in the fifth.
Whyte needed treatment but will get a rematch according to Eddie Hearn.
Reaction to shock Whyte knockoutTaylor wins relentless Persoon rematch"I can't quite believe it," said promoter Hearn. "When the punch landed I felt like I was in some dream. The fight was over virtually. Dillian was measuring Povetkin up, then two heavy knockdowns.
"I and others thought it was over. This is the drama of heavyweight boxing, one punch can change everything.
"He has to do a job in a rematch."
Povetkin, who has only lost to Wladimir Klitschko and IBF, WBO and WBA world heavyweight champion Anthony Joshua in a 39-fight and 15-year-long career, simply found "the best punch he has ever thrown" according to BBC Radio 5 Live's Steve Bunce.
The obscure and fan-free surroundings in the garden of Matchroom Boxing's headquarters allowed the hysterical celebrations of Povetkin's team to rumble through the night air while Whyte was almost motionless on his back.
The British heavyweight had been almost punch perfect for 12 minutes. Shots to the body drew red marks on Povetkin, while jabs pawed at the Russian's face looked to be discouraging the dangerous bookmakers' underdog.
Two hard right hands and a short left hook combined sweetly to floor Povetkin in the fourth and, before the bell, Whyte drove home a left uppercut when backed to the ropes to send his rival down again.
But moments later the tables turned and Povetkin dipped to his left and thrust an uppercut of his own on to Whyte's chin. From nowhere, he found a way to hit back at those who felt his time had been and gone.
Since his only defeat - to Joshua in 2015 - Whyte has put solid names on his record and seen them off one by one when he could have taken more straightforward assignments.
His refusal to simply sit and wait for his chance endeared him as a risk taker to fans and undoubtedly improved him as an athlete and fighter.
But one punch ultimately made this a risk too far and Whyte must now go to work once again if he is to rediscover hope of a first world-title shot.
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