Carl Froch clambered up from a shocking first-round knockdown to retain his WBA and IBF super-middleweight titles with a controversial ninth-round stoppage of George Groves in Manchester.
Froch was floored by a flinging right hand in the opening moments but clawed his way back into the bout and won a spectacular duel when referee Howard Foster jumped in to end the contest in the ninth.
Foster's intervention with Groves still on his feet sparked uproar, with both corner teams briefly squaring off in the ring while a crowd which had started off resolutely pro-Froch roundly cheered the challenger.
Questions were inevitably raised about the eagerness of Foster to end the fight which had rocked and rolled from one fighter to the other and produced some of the finest action seen in a British ring for some time.
Froch was staggered on his feet in a sensational sixth before retaliating with big shots of his own, and the ending when it came seemed premature but in Foster's favour Groves did appear to be offering little resistance.
Froch may have mocked Groves' credentials for sharing the same ring during the acrimonious big-fight build-up and appeared to believe he was due an easy and enjoyable night - but it proved anything but.
Groves had revealed intricate details of how he planned to take the fight to Froch but it was clear from the outset he would also be up against the vast majority of the 20,000-capacity crowd who booed him to the ring.
The action came to a clattering and sudden end in the ninth when after a close-quarters exchange Groves appeared to turn his back and drop his hands, and as Froch poured in unanswered punches referee Foster quickly jumped in to end the contest.
Boos rang down from the capacity crowd when the verdict was announced, sealing a remarkable turnaround for brave Groves who exited to a hero's ovation.