Dillian Whyte took his record to 24-1 as he survived a late barrage to beat Joseph Parker on points at London's O2.
A brilliant fight saw both men hit the canvas but it was Whyte's early aggression which earned him a unanimous verdict on the cards.
Parker emerged with great credit, getting up from what might otherwise have been a fight-winning left from Whyte in the ninth round to end the fight on the front foot.
Indeed, the New Zealander put his opponent down late in the final round and would surely have ended the fight granted another minute, but Whyte clung on bravely for a hard-fought success.
Prior to Saturday's fight, which he started as a narrow favourite, Parker had never before hit the canvas but that changed early on, although replays showed it was a clash of heads rather than a clean shot.
Whyte, though, was the clear aggressor throughout and finally made a breakthrough in the ninth, a clubbing hook sending Parker crashing to the canvas.
To his credit, the 26-year-old was up quickly to face the count and saw out the remainder of the round, but his corner were clearly concerned and with good reason, as Whyte prepared to go to war again.
Parker was at last able to counter in the 10th, where Whyte was warned after a shoulder tackle almost forced his opponent over the top rope, and in the 11th he had his man rocked for the first time.
A big right from Parker in the final round again had Whyte in serious trouble and finally he was down with half a minute left, but having made the count the 30-year-old clung on for a clear points win.
"I messed up at the final hurdle," said Whyte. "I went down, I got rocked, I took a knee. I'm still learning."
Parker, magnanimous in defeat, added: "Thanks for having us. What a great opportunity it is to come back and fight in the UK.
"I got 12 rounds to fight, gave it my best, better man won."