Nottingham fighter Leigh Wood pulled off a shock victory to stop Xu Can in the final round and claim the WBA featherweight world title at the Matchroom Fight Camp in Brentwood.
Xu was returning to action for the first time since outpointing Manny Robles III in November 2019 and his ring rust showed as 32-year-old Wood produced a superb controlled display.
Behind on the cards heading into the final round, the champion needed a big finish – but was put onto the canvas by another powerful right hook from Wood before the referee stepped in to end the contest.
Wood, 32, had came out on the front foot, landing a flowing combination of body shots during the opening stages.
Xu, undefeated since 2014, was left with a blooded nose following a swift uppercut by Wood in the third.
The Beijing fighter finally found his range to step up the work rate in the fifth and dragged himself back into the contest.
Wood, though, powered on again in the eighth, switching stances to rattle the champion and regain some momentum heading into the closing rounds.
The Briton showed no signs of letting up as Xu also tried to raise the tempo in the 11th, but it was Wood who produced the telling blow, dropping the champion in the final round before swiftly sending him onto the ropes again before the referee stepped in.
Wood, who took the fight at short notice, could now be in line for an all-British showdown with Josh Warrington, who has a rematch against Mauricio Lara in September in Leeds.
"(Trainer) Ben Davison (trainer) was my key. The tactics I came up with. It's physics, if you keep getting hit, you are going to go down basically," Wood said on BBC Radio 5 Live.
"You have to be smart, mix it up and we had a game-plan that Ben gave me."
"He was taking some big shots all the way through the fight. They took their toll. He didn't go down early enough, and I kept seeing him wincing and he didn't like the shots, but credit, he's so tough."
Wood added: "I had six weeks' notice for that fight. I can get even fitter than that.
"I had to be smart knowing I only had six weeks' (preparation). I knew I was ahead (on the judges' cards), credit to him and I want to be in some big fights."
Earlier in Essex, Chris Billam-Smith had earlier edged out Tommy McCarthy on a split decision to add the British and European Cruiserweight titles to his Commonwealth crown after 12 bruising rounds.
Irishman McCarthy battled on after being cut following a clash of heads during the sixth, but it was Billam-Smith who took the judges scores by 116-112 and 115-114 to 114-115.
Elsewhere on the undercard, Anthony Fowler stopped German Rico Mueller in the eighth round of their super-welterweight contest.
Afterwards, it was announced the 30-year-old would next face fellow Liverpool fighter Liam Smith in their home town on October 9.
Campbell Hatton, son of former double world champion Ricky, delivered a four-round points win over Polish boxer Jakub Laskowski to extend his unbeaten record through three fights.
Jack Cullen secured the IBF international super-middleweight title with a 10-round unanimous decision over Avni Yildirim.
Sandy Ryan, who won gold at the 2018 Commonwealth Games, made a successful professional debut with a points win over Kirstie Bavington in their six-round super-lightweight contest.
Conor Benn had been set to defend his WBA continental welterweight against Adrian Granados, but Saturday's original headline bout was postponed after the British boxer tested positive for Covid-19.