Junior Witter put in a patchy display in Los Angeles to beat South Africa's Lovemore N'Dou on points and defend his Commonwealth light welterweight title.
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Fighting on the undercard of Howard Eastman's bout with Bernard Hopkins, the Briton had promised an explosive show for the American public.
And he delivered early on, putting respected N'Dou on the canvas twice.
But the challenger battled back gamely before getting caught by a left hook in round 10 and Witter held on to win.
Witter, 30, had started confidently and looked to have ample ammunition to end the contest early when he sent his opponent down with huge blows in rounds three and four.
N'Dou showed trademark resolve to get back up on both occasions and then dominated the middle rounds as Witter visibly tired.
And in the final rounds, the Briton drew a few boos from the Staples Center crowd as he tried to stay out of trouble.
A peach of a left hook almost ended N'Dou's resistance late on before Witter tried to finish in style with a looping attempt at a knockout punch.
His post-fight celebration sommersault belied an inconsistent and sometimes weary performance.
But Witter just about deserved his victory - 114-112 on two cards and 115-111 on the other - and improved his pro record to 31 wins, one loss and two draws.
Afterwards, Witter blamed a hand injury for his loss of form.
"I hurt my hand so I had to change my style a bit but I was always in control and I didn't think I lost a round.
"I really thought I gave an excellent display.
"People asked how I was going to cope going 12 rounds against a world-class opponent who has only gone down once in his whole career.
"I went out there and knocked him down twice and clearly won the fight - my timing was a bit off and I wasn't 100% but I did enough to beat him."
Witter labelled the left uppercut which decked N'Dou for the first time in the third round one of the best punches thrown of his career.
"N'Dou was very tough but if it wasn't for the end of the round I might have finished him.
"The bell saved him but his recovery was absolutely brilliant. He is a very, very, very tough man."