Kal Sajad
BBC Sport journalist
Artur Beterbiev beat Dmitry Bivol by majority decision to become the undisputed light-heavyweight world champion as one of boxing's most-anticipated fights lived up to the hype in Saudi Arabia.
In a contest that could have gone either way, Bivol, 33, won the earlier rounds with his superior movement and combinations.
Fellow undefeated Russian Beterbiev, 39, was undeterred and forced his way back into the fight with relentless pressure and power punching.
With scores of 114-114, 115-113 and 116-112, Beterbiev becomes the division's first undisputed champion since 2002, and the first ever in the four-belt era.
"I feel not bad. I did not good today. I wanted to box with more quality," said a modest Beterbiev - who is now WBC, WBA (Super), IBF and WBO champion.
Bivol was defeated for the first time in 24 bouts.
"I am a warrior. I don't know, I did my job but I felt like I could do better but it was just the opinion of some judges," he said.
In the chief support, Fabio Wardley retained the British heavyweight title with a spectacular first-round stoppage win over Frazer Clarke in a rematch of March's fight-of-the-year contender.
Wardley, 29, landed a heavy, looping right hand to hurt the challenger and floored him with another ferocious right.
A dazed Clarke admirably rose to his feet but was in no position to continue as the referee halted the contest.
A fight for the purist delivers on the hype
Two unbeaten champions with differing but equally effective styles produced a match-up of the highest level in a fight to make the boxing purist salivate.
A watchful Bivol shone early on as he circled around the ring, working behind the jab and landing smart combinations.
Despite his menacing power, two-time Olympian Beterbiev's boxing skills often go under the radar. He continued to walk Bivol down and landed a vicious body shot in the fifth.
Just when it appeared Bivol was tiring, he responded with a flurry of shots to momentarily stem the pressure, but Beterbiev would not back down.
Both champions were hurt in a terrific seventh. A combination from Bivol stunned Beterbiev, who sprung into action seconds later to end the round with some ferocious power shots.
Beterbiev's corner told him he needed a knockdown as the fight entered the championship rounds.
"They always say that. I was more focused but not more aggressive," he said post-fight.
He could not find the finishing punch to maintain his perfect knockout record but ended the fight on top, winning rounds 10, 11 and 12 on all three judges scorecards.
Beterbiev has not only proved his worth as the best pugilist of his division, he has entertained his way to the top of the summit.
His historic win in the Middle East undoubtedly cements his place as an all-time light-heavyweight great.
In such a close and entertaining fight, however, there will be a clamouring from the boxing fraternity for a rematch.
Wardley cleans out Clarke in one round
Wardley and Clarke could not be split in their all-action first fight on Easter Sunday, but the rematch was as clinical as it comes.
Olympian Clarke leaned on his amateur grounding with a smart double jab in the first minute but Wardley – who contested just a handful of unlicensed white collar bouts before turning pro – unleashed the raw power to score his 17th stoppage in 18 wins.
"I've got dynamite power in each hand. Once I've hurt someone, I know I can get rid of them," unbeaten Wardley – who won his 18th pro fight – said.
Clarke received medical assistance in the ring before heading over to congratulate the champion. The 2020 Olympic bronze medallist left before the result was announced.
"I can't help it, war by name and war by nature," Wardley said. "Once I have my enemies hurt, there's no help for them unless the bell rings."
He now surpasses domestic level and plans to set upon a path towards world level.
With Wardley and IBF champion Daniel Dubois, and prospects such as Moses Itauma, the future looks bright for British heavyweight boxing.