Sergey Kovalev (34-3-1) survived an eighth-round scare to knock out Anthony Yarde (18-1) in the11th round to defend his WBO world light-heavyweight title in a thrilling fight.
Russia's Kovalev, 36, dominated early on in his home city of Chelyabinsk, with his vaster experience over the 18-0 novice, but came close to being beaten in the eighth stanza when he was subject to a relentless attack from 'The Beast from the East'.
Yarde looked to be on the brink of glory but the champion's experience and know-how somehow got him through.
Despite being fatigued himself Kovalev responded well and pounced on a tiring Yarde to land an 11th-round knockout.
In what was his first world-title shot, Yarde will look back on an eighth round in which his promoter Frank Warren said he was "seconds away" from a colossal shock.
As the bell sounded, Kovalev's promoter Egis Klimas could be seen puffing out his cheeks, seemingly relieved that hope of a lucrative bout with Saul 'Canelo' Alvarez next remained alive.
Reflecting on how close he came Yarde, 28, said: "I hurt him to the body, I thought I should go for it and my corner said so, so we went for it.
"I am not ashamed or embarrassed, I am ambitious and trying to motivate people to go for what you want.
"I have done myself justice, even coming out here - 99% of people would not have dared to do what I did. Experience played a big part, he paced himself better."
Kovalev - a three-time world champion at light-heavyweight - has contested global titles in his last 16 fights, a run dating back to his demolition of Wales' Nathan Cleverly in Cardiff in 2013.
Yarde in contrast entered the contest after just 12 amateur and 18 professional fights and the London fighter had never gone past seven rounds.
Many in boxing questioned how good he was based on the calibre of opposition he had faced, while his trainer Tunde Ajayi has faced criticism for stating he does not endorse sparring in preparation.
Yarde, though, undoubtedly answered questions, notably over whether he could absorb punishment against a top-class fighter.
Kovalev, cheered to the ring in his first fight in Russia since 2016, controlled the first half of the contest, his greater experience and a sharp jab to head and body proving the difference.
But in the eighth, with Kovalev appearing fatigued, Yarde landed heavily and chased his rival, who was backed to the ropes and on unsteady legs before the bell.
Kovalev's trainer Buddy McGirt told him he would end the fight if he took similar punishment again and his fighter responded brilliantly, hitting and moving in the ninth before appearing close to stopping Yarde in the 10th.
Yarde's efforts in the eighth round looked to have emptied his own tank and while he gallantly strode forward in the 11th, he walked on to a shot which ultimately extended Kovalev's record to 34 wins, three losses and a draw.
Afterwards Kovalev said Yarde will "100%" become a world champion but he too deserves huge credit for coming through a test which looks set to pave the way for a fight with Alvarez - the world's best-paid fighter - in November.